Influenza vaccination coverage among US children from 2004/2005 to 2015/2016

Influenza vaccination coverage among US children from 2004/2005 to 2015/2016 Abstract Background Quantify the influenza vaccine coverage is essential to identify emerging concerns and to immunization programs for targeting interventions. Methods Data from National Health Interview Survey were used to estimate receipt of at least one dose of influenza vaccination among children 6 months to 17 years of age. Results Influenza vaccination coverage increased from 16.70% during 2004/2005 to 49.43% during 2015/2016 (3.18% per year, P < 0.001); however, the coverage increased slightly after 2010/2011. Children at high risk of influenza complications had higher influenza vaccination coverage than non at-risk children. Boys and girls had similar coverage each year. While the coverage increased from 2004/2005 to 2015/2016 for all age groups, the coverage decreased with age each year (−0.64 to −1.58% per age group). There was a higher and rapid increase of coverage in Northeast than Midwest, South and West. American Indian or Alaskan Native and Asian showed higher coverage than other race groups (White, Black/African American, Multiple race). Multivariable analysis showed that high-risk status and region had the greatest associations with levels of vaccine coverage. Conclusions Although the influenza vaccination coverage among children had increased remarkably since 2004/2005, establishing more effective immunization programs are warranted to achieve the Healthy People 2020 target. children, coverage, influenza vaccine Introduction Influenza is a common pathogen identified in children with acute lower respiratory infections and results in a substantial burden on health services worldwide.1,2 Historically, 80–85% of pediatric deaths have occurred in unvaccinated children 6 months and older in USA.3 Vaccination remains the best available preventive measure against influenza, although the effectiveness of influenza vaccination can vary considerably from year to year.4 The American Academy of Pediatrics recommends that all children 6 months of age and older receive influenza vaccine each year, especially those at high risk of influenza complications.3 Both universal programs and targeted programs are available to promote the coverage of influenza vaccine among children.5 Observational data from the Influenza Vaccine Effectiveness Network revealed that quadrivalent live attenuated influenza vaccine performed poorly against influenza A (H1N1)pdm09 viruses in recent influenza seasons. Therefore, quadrivalent live attenuated influenza vaccine is not recommended for use in any setting in the USA since 201 6.3,4 In USA, insurance plans cover the cost of influenza vaccines for free, and those have no health insurance coverage could also receive influenza vaccines for free with the Vaccines for Children Program. Influenza vaccines are offered by many doctor’s offices, clinics, health departments, pharmacies, college health centers and even by some schools. The US Healthy People 2020 sets a target of 70% vaccination coverage of children 6 months to 17 years overall against influenza annually.6 The National Health Interview Survey (NHIS) has been considered the most representative source for estimates of influenza vaccination coverage among children aged 6 months to 17 years and has served as the Healthy People data source for influenza vaccination estimates.6 Quantifying the influenza vaccine coverage in recent years would be useful to immunization programs for targeting interventions and could help guide public health action to improve full influenza vaccination coverage. Therefore, based on the NHIS, the objective of this study was to quantify the influenza vaccination coverage among children aged 6 months to 17 years from 2004/2005 to 2015/2016, overall, by age, gender, region, race/ethnicity and high-risk status. Materials and methods This paper was reported in accordance with the following the STROBE checklist items. The NHIS is the principal source of information on the health of the civilian non-institutionalized US population. The NHIS is a cross-sectional household face-to-face interview survey, and interviewing is continuous throughout each year. The sample design follows a multistage area probability design. From each family in the NHIS, one ‘sample child’ aged 17 years or less is randomly selected (if any children are in the family). Information about the sample child is collected from a knowledgeable adult. The Child Influenza Immunization was included for the first time in the 2005 NHIS. Questions included receipt of a flu vaccination in the past 12 months; month and year of the most recent flu vaccination; receipt of nasal flu spray vaccination in the past 12 months; and month and year of most recent nasal flu spray vaccination. Flu shot and flu nasal spray items were provided separately in the datasets before 2009/2010, and seasonal flu instead of flu was inquired to distinguish it from the pH1N1 vaccine during 2009/2010. The response rates for the sample child component taking into account the overall family response rate for 2004/2005 through 2015/2016 were 77.5, 78.8, 76.5, 72.3, 73.4, 70.7, 74.6, 69.7, 69.0, 66.6, 63.4 and 67.1%, respectively. Weights were used for design, ratio, non-response and post-stratification adjustments for sample children, from which national estimates of all sample child variables can be made. The total final annual weights from 2004/2005 to 2015/2016 were 73 375 618, 73 493 430, 73 727 832, 73 858 887, 73 995 812, 74 626 232, 74 518 100, 73 661 368, 73 485 749, 73 407 881, 73 453 101 and 73 565 825, respectively. Influenza vaccination coverage as well as its 95 confidence interval (95% CI) during each period were provided.7 Tests for linear trend across periods (2004/2005 to 2015/2016, i.e. slope) were performed using a weighted linear regression on the period-specific estimates, using period number as the independent variable and weights as the inverse of the estimated variance of the estimated vaccination coverage. High-risk status was defined based on parental report of one or more of the following: ever being told by a physician that the child had cystic fibrosis, sickle cell anemia, diabetes, congenital heart disease, other heart conditions, cerebral palsy, muscular dystrophy and seizures; or reporting an asthma episode or attack in the past 12 months (i.e. current asthma).3,8 Subgroup analysis were conducted by high-risk status, gender, age, region (Northeast, Mideast, South, West), ethnicity (Hispanic or not) and race [American Indian or Alaskan Native (AIAN), Asian, White, Black/African American, Multiple race]. Univariate logistic analysis was conducted to test whether influenza vaccine coverage is statistically different between groups. To assess which demographics characteristics have the greatest associations with levels of influenza vaccine coverage while adjusting for other variables, multivariable logistic analysis were conducted including high-risk status, gender, age, region, ethnicity, race, family income and education of adult with the highest education in family. Region and race were included as indicator variables in logistic analysis. The NHIS was approved by the Research Ethics Review Board of the National Center for Health Statistics. Stata 12.0 was used, and P < 0.05 was considered statistically significant. Results As shown in Table 1, influenza vaccination coverage (at least one dose) increased from 16.70% (95% CI: 16.05–17.38%) during 2004/2005 to 49.43% (48.48–50.38%) during 2015/2016, and the average annual increase was 3.18% (P < 0.001) based upon the slope of the trend test; however, the coverage increased slightly after 2010/2011. Children at high risk of influenza complications had higher influenza vaccination coverage than non at-risk children each year, and the coverage was 59.15% (55.44–62.80%) and 48.74% (47.76–49.73%) during 2015/2016 among those with and without high-risk conditions, respectively. Boys and girls had similar coverage each year and similar annual increase. While the coverage increased from 2004/2005 to 2015/2016 for all age groups, the coverage decreased with age each year (−0.64 to −1.58% per age group, P < 0.001). There was a higher coverage in Northeast than Midwest, South and West each year, and the coverage was 59.29% (56.95–61.60%), 46.66% (44.57–48.76), 45.73% (44.14–47.33) and 50.44% (48.62–52.26%) during 2015/2016, respectively. No obvious difference was found by ethnicity (Hispanic or not). However, in subgroup by race, AIAN and Asian showed higher coverage than other race groups (White, Black/African American, Multiple race), and the coverage was 61.54% (53.76–68.91%), 64.74% (60.78–68.55%), 48.16% (47.06–49.27%), 46.96% (44.24–49.70%) and 51.90% (47.92–55.86%), respectively. Administration methods included flu shot and flu nasal spray, and the percentage of flu shot ranged from 79.33 to 96.70% during the study period. Table 1 Influenza vaccination coverage (at least one dose) among children aged 6 months–17 years in the NHIS, 2004/2005 through 2015/2016 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Table 1 Influenza vaccination coverage (at least one dose) among children aged 6 months–17 years in the NHIS, 2004/2005 through 2015/2016 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Overall, univariate logistic analysis showed that vaccine coverage was statistically different in stratified analysis by high-risk status, age, region and race, while no significant difference was found in stratified analysis by gender and ethnicity. Findings from multivariable analysis (Table 2) showed that high-risk status and region had the greatest associations with levels of vaccine coverage while adjusting for other variables. Age was consistently associated with levels of influenza vaccine coverage across all periods. In addition, compared with the white race group, races of AIAN, Asian Black/African American and multiple race showed a higher likelihood of influenza vaccination receipt, although the differences were not significantly in several periods. Table 2 Multivariable analysis between demographics characteristics and levels of influenza vaccine coverage among children aged 6 months–17 years Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 OR, odds ratio. Table 2 Multivariable analysis between demographics characteristics and levels of influenza vaccine coverage among children aged 6 months–17 years Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 OR, odds ratio. Discussion Main finding of this study Data from the NHIS showed a continuous growth in influenza vaccination coverage from 2004/2005 to 2010/2011, but the coverage increased slightly thereafter among US children aged 6 months to 17 years. No obvious difference was observed by gender and ethnicity, but at-risk children, children in Northeast and race groups of AIAN and Asian had higher influenza vaccination coverage. In addition, the influenza vaccination coverage decreased with age across each year. Multivariable analysis showed that high-risk status and region had the greatest associations with levels of vaccine coverage while adjusting for other variables. What is already known on this topic Potential explanations for the observed trend after 2010/2011 are mainly unclear. Influenza A (H1N1) and influenza A (H3N2) viruses predominated since 2007/2008 in USA, and the majority of circulating strains matched vaccine strains well.3 While pediatric hospitalizations and deaths caused by influenza vary by the predominant circulating strain and from one season to the next, the adverse events (92–171 pediatric deaths; 41.4–67 hospitalizations per 100 000 for 0–4 years old; 9.4–16.6 hospitalizations per 100 000 for 5–17 years old) were relatively stable since 2012/20 13.3 However, lowest adverse events were observed during 2011/2012 (37 pediatric deaths; 16 hospitalizations per 100 000 for 0–4 years old; 4 hospitalizations per 100 000 for 5–17 years old) while a peak was observed during 2009/2010 (288 pediatric deaths; 77.7 hospitalizations per 100 000 for 0–4 years old; 27.2 hospitalizations per 100 000 for 5–17 years old).3 Withdrawal of the live attenuated influenza vaccine recommendation was not associated with an overall change in child influenza immunization rates across seasons.9 In addition, children’s likelihood of following immunization recommendations was associated with the immunization behavior of their parents.10 Therefore, for a better understanding of our findings, it would be helpful to analysis the trend of influenza vaccination coverage in their parents in future, and encouraging parental immunization is a potential tool for increasing children’s immunization rates.10,11 The perspective, programmatic design, setting, and inclusion of herd immunity affected cost-effectiveness,5 and immunization programs using group administration are more cost-effective than programs using individual administration.5,12,13 Furthermore, common factors that influence the implementation of programs were also indentified, including program leadership and governance, organizational models and institutional relationships, workforce capacity and roles particularly concerning the school nurse, communication with parents and students.14 What this study adds Higher influenza vaccination coverage was found among high-risk children and AIAN children, probably in part because special efforts are recommended to vaccinate these children3. Boys and girls had similar influenza vaccination coverage in this analysis, which was consistent with the findings from National Immunization Survey-Flu for the 2012–13 and 2013–14 influenza seasons.15 Health-care access was found to have a robust and positive association with vaccination rates for both children and adults,16 which may partially explain the decreased trend in influenza vaccination coverage with age, because younger children tend to have more frequent visits to health-care institutions and are at increased risk of hospitalization and complication. The difference in coverage by region of residence was consistent with 2008 National Immunization Survey.17 Based on 2012 NHIS for adults, Lu et al.18 also found relatively low influenza vaccination coverage in non-Hispanic black and a relatively high coverage in non-Hispanic Asia. Furthermore, this analysis also showed that, after adjusting for other variables simultaneously, high-risk status and region had the greatest associations with levels of vaccine coverage and age was consistently associated with levels of influenza vaccine coverage across all periods. In addition, race should also contribute to the levels of influenza vaccination. Limitations of this study Strength of this study included the continuous analysis of the influenza vaccination coverage from 2004/2005 to 2010/2011, and subgroups analysis were conducted by risk status, gender, age, region of residence, race and ethnicity. The findings are also subject to limitations. First, influenza vaccination coverage was based on parental report and may be subject to recall bias. Thus analysis of provider report of influenza vaccination coverage among children should be useful in future. Second, the number of influenza vaccine doses to be administered depends on the child’s age and vaccine history. Children 6 months through 8 years of age may need two doses depending on the child’s vaccine history. Given detailed influenza vaccine history was not available, full vaccination coverage among children aged 6 months–8 years was not assessed in this analysis. However, the percentage of children aged 6 months–8 years who were fully vaccinated against influenza for 2012/2013 and 2013/2014 based on parental report in US has been reported recently with the National Immunization Survey-Flu,15 and the percentages during the 2012/2013 and 2013/2014 were 41.0 and 45.2%, respectively. In addition, among those children who required two doses, about half received at least one dose in 2012/2013 and 2013/2014, suggesting that there are barriers to receipt of the second required dose.15 Finally, the response rate declined over time from 2004/2005 to 2015/2016, and healthy user bias may be of concern. However, as described in the NHIS Description, final annual weights were considered that includes design, ratio, non-response and post-stratification adjustments for sample children, and national estimates of all sample child variables can be made using these weights. Therefore, non-response should not be a major concern for this type of analysis. Conclusions In summary, while there was a continuous growth in influenza vaccination coverage from 2004/2005 to 2010/2011, the coverage increased slightly thereafter among US children aged 6 months to 17 years. More effective influenza immunization policies and programs are warranted to achieve the Healthy People 2020 target of 70% for children 6 months to 17 years. In addition to the high-risk status, region, age and even race should be considered to further promote the coverage of influenza vaccine among children. Conflict of interest None. Acknowledgements None. Funding This work was supported by Kunshan Special Fund for Social Development and Science & Technology (No.: 001ZX07) and Suzhou ‘Kejiaoxingwei’ Youth Science Project (No.: KJXW2017073). Role of funding The sponsors have no role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. Contributors The authors’ contributions to the present study were as follows: TCW and WH contributed to data collection and did the data analyses and drafted the article. WWM and LXM revised the article. TCW and LXM are responsible for the whole work. All authors have read and approved of the final version of the article. References 1 Nair H , Brooks WA , Katz M et al. . Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis . Lancet 2011 ; 378 : 1917 – 30 . Google Scholar CrossRef Search ADS PubMed 2 Lafond KE , Nair H , Rasooly MH et al. . Global role and burden of influenza in pediatric respiratory hospitalizations, 1982–2012: a systematic analysis . PLoS Med 2016 ; 13 : e1001977 . Google Scholar CrossRef Search ADS PubMed 3 COMMITTEE ON INFECTIOUS DISEASES . Recommendations for prevention and control of influenza in children, 2017–2018 . Pediatrics 2017 ; 140 : e20172550 . CrossRef Search ADS PubMed 4 Jackson ML , Chung JR , Jackson LA et al. . Influenza vaccine effectiveness in the United States during the 2015–2016 season . N Engl J Med 2017 ; 377 : 534 – 43 . Google Scholar CrossRef Search ADS PubMed 5 Ting EEK , Sander B , Ungar WJ . Systematic review of the cost-effectiveness of influenza immunization programs . Vaccine 2017 ; 35 : 1828 – 43 . Google Scholar CrossRef Search ADS PubMed 6 Office of Disease Prevention and Health Promotion (US) . Healthy People 2020: Topics & Objectives—Immunization and Infectious Diseases [cited 2017 Nov. 16]. https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectives. 7 Brown LD , Cai TT , DasGupta A . Interval estimation for a binomial proportion . Stat Sci 2001 ; 16 : 101 – 17 . 8 Santibanez TA , Lu PJ , O’Halloran A et al. . Trends in childhood influenza vaccination coverage—U.S., 2004–2012 . Public Health Rep 2014 ; 129 : 417 – 27 . Google Scholar CrossRef Search ADS PubMed 9 Robison SG , Dunn AG , Richards DL et al. . Changes in influenza vaccination rates after withdrawal of live vaccine . Pediatrics 2017 ; 140 : e20170516 . Google Scholar CrossRef Search ADS PubMed 10 Robison SG , Osborn AW . The concordance of parent and child immunization . Pediatrics 2017 ; 139 : e20162883 . Google Scholar CrossRef Search ADS PubMed 11 Yeung MP , Lam FL , Coker R . Factors associated with the uptake of seasonal influenza vaccination in adults: a systematic review . J Public Health (Oxf) 2016 ; 38 : 746 – 53 . Google Scholar PubMed 12 Rai GK , Wood A . Effectiveness of community pharmacies in improving seasonal influenza uptake-an evaluation using the Donabedian framework . J Public Health (Oxf) 2017 : 1 – 7 . 13 Hashmi S , D’Ambrosio L , Diamond DV et al. . Preventive behaviors and perceptions of influenza vaccination among a university student population . J Public Health (Oxf) 2016 ; 38 : 739 – 45 . Google Scholar PubMed 14 Perman S , Turner S , Ramsay AI et al. . School-based vaccination programmes: a systematic review of the evidence on organisation and delivery in high income countries . BMC Public Health 2017 ; 17 : 252 . Google Scholar CrossRef Search ADS PubMed 15 Zhai Y , Santibanez TA , Kahn KE et al. . Parental-reported full influenza vaccination coverage of children in the U.S . Am J Prev Med 2017 ; 52 : e103 – 13 . Google Scholar CrossRef Search ADS PubMed 16 Chiu APY , Dushoff J , Yu D et al. . Patterns of influenza vaccination coverage in the United States from 2009 to 2015 . Int J Infect Dis 2017 ; 65 : 122 – 7 . Google Scholar CrossRef Search ADS PubMed 17 Schuller KA , Probst JC . Factors associated with influenza vaccination among US children in 2008 . J Infect Public Health 2013 ; 6 : 80 – 8 . Google Scholar CrossRef Search ADS PubMed 18 Lu PJ , O’Halloran A , Williams WW et al. . Racial and ethnic disparities in vaccination coverage among adult populations in the U.S . Vaccine 2015 ; 33 ( Suppl 4 ): D83 – 91 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Public Health Oxford University Press

Influenza vaccination coverage among US children from 2004/2005 to 2015/2016

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com
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1741-3842
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1741-3850
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10.1093/pubmed/fdy081
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Abstract

Abstract Background Quantify the influenza vaccine coverage is essential to identify emerging concerns and to immunization programs for targeting interventions. Methods Data from National Health Interview Survey were used to estimate receipt of at least one dose of influenza vaccination among children 6 months to 17 years of age. Results Influenza vaccination coverage increased from 16.70% during 2004/2005 to 49.43% during 2015/2016 (3.18% per year, P < 0.001); however, the coverage increased slightly after 2010/2011. Children at high risk of influenza complications had higher influenza vaccination coverage than non at-risk children. Boys and girls had similar coverage each year. While the coverage increased from 2004/2005 to 2015/2016 for all age groups, the coverage decreased with age each year (−0.64 to −1.58% per age group). There was a higher and rapid increase of coverage in Northeast than Midwest, South and West. American Indian or Alaskan Native and Asian showed higher coverage than other race groups (White, Black/African American, Multiple race). Multivariable analysis showed that high-risk status and region had the greatest associations with levels of vaccine coverage. Conclusions Although the influenza vaccination coverage among children had increased remarkably since 2004/2005, establishing more effective immunization programs are warranted to achieve the Healthy People 2020 target. children, coverage, influenza vaccine Introduction Influenza is a common pathogen identified in children with acute lower respiratory infections and results in a substantial burden on health services worldwide.1,2 Historically, 80–85% of pediatric deaths have occurred in unvaccinated children 6 months and older in USA.3 Vaccination remains the best available preventive measure against influenza, although the effectiveness of influenza vaccination can vary considerably from year to year.4 The American Academy of Pediatrics recommends that all children 6 months of age and older receive influenza vaccine each year, especially those at high risk of influenza complications.3 Both universal programs and targeted programs are available to promote the coverage of influenza vaccine among children.5 Observational data from the Influenza Vaccine Effectiveness Network revealed that quadrivalent live attenuated influenza vaccine performed poorly against influenza A (H1N1)pdm09 viruses in recent influenza seasons. Therefore, quadrivalent live attenuated influenza vaccine is not recommended for use in any setting in the USA since 201 6.3,4 In USA, insurance plans cover the cost of influenza vaccines for free, and those have no health insurance coverage could also receive influenza vaccines for free with the Vaccines for Children Program. Influenza vaccines are offered by many doctor’s offices, clinics, health departments, pharmacies, college health centers and even by some schools. The US Healthy People 2020 sets a target of 70% vaccination coverage of children 6 months to 17 years overall against influenza annually.6 The National Health Interview Survey (NHIS) has been considered the most representative source for estimates of influenza vaccination coverage among children aged 6 months to 17 years and has served as the Healthy People data source for influenza vaccination estimates.6 Quantifying the influenza vaccine coverage in recent years would be useful to immunization programs for targeting interventions and could help guide public health action to improve full influenza vaccination coverage. Therefore, based on the NHIS, the objective of this study was to quantify the influenza vaccination coverage among children aged 6 months to 17 years from 2004/2005 to 2015/2016, overall, by age, gender, region, race/ethnicity and high-risk status. Materials and methods This paper was reported in accordance with the following the STROBE checklist items. The NHIS is the principal source of information on the health of the civilian non-institutionalized US population. The NHIS is a cross-sectional household face-to-face interview survey, and interviewing is continuous throughout each year. The sample design follows a multistage area probability design. From each family in the NHIS, one ‘sample child’ aged 17 years or less is randomly selected (if any children are in the family). Information about the sample child is collected from a knowledgeable adult. The Child Influenza Immunization was included for the first time in the 2005 NHIS. Questions included receipt of a flu vaccination in the past 12 months; month and year of the most recent flu vaccination; receipt of nasal flu spray vaccination in the past 12 months; and month and year of most recent nasal flu spray vaccination. Flu shot and flu nasal spray items were provided separately in the datasets before 2009/2010, and seasonal flu instead of flu was inquired to distinguish it from the pH1N1 vaccine during 2009/2010. The response rates for the sample child component taking into account the overall family response rate for 2004/2005 through 2015/2016 were 77.5, 78.8, 76.5, 72.3, 73.4, 70.7, 74.6, 69.7, 69.0, 66.6, 63.4 and 67.1%, respectively. Weights were used for design, ratio, non-response and post-stratification adjustments for sample children, from which national estimates of all sample child variables can be made. The total final annual weights from 2004/2005 to 2015/2016 were 73 375 618, 73 493 430, 73 727 832, 73 858 887, 73 995 812, 74 626 232, 74 518 100, 73 661 368, 73 485 749, 73 407 881, 73 453 101 and 73 565 825, respectively. Influenza vaccination coverage as well as its 95 confidence interval (95% CI) during each period were provided.7 Tests for linear trend across periods (2004/2005 to 2015/2016, i.e. slope) were performed using a weighted linear regression on the period-specific estimates, using period number as the independent variable and weights as the inverse of the estimated variance of the estimated vaccination coverage. High-risk status was defined based on parental report of one or more of the following: ever being told by a physician that the child had cystic fibrosis, sickle cell anemia, diabetes, congenital heart disease, other heart conditions, cerebral palsy, muscular dystrophy and seizures; or reporting an asthma episode or attack in the past 12 months (i.e. current asthma).3,8 Subgroup analysis were conducted by high-risk status, gender, age, region (Northeast, Mideast, South, West), ethnicity (Hispanic or not) and race [American Indian or Alaskan Native (AIAN), Asian, White, Black/African American, Multiple race]. Univariate logistic analysis was conducted to test whether influenza vaccine coverage is statistically different between groups. To assess which demographics characteristics have the greatest associations with levels of influenza vaccine coverage while adjusting for other variables, multivariable logistic analysis were conducted including high-risk status, gender, age, region, ethnicity, race, family income and education of adult with the highest education in family. Region and race were included as indicator variables in logistic analysis. The NHIS was approved by the Research Ethics Review Board of the National Center for Health Statistics. Stata 12.0 was used, and P < 0.05 was considered statistically significant. Results As shown in Table 1, influenza vaccination coverage (at least one dose) increased from 16.70% (95% CI: 16.05–17.38%) during 2004/2005 to 49.43% (48.48–50.38%) during 2015/2016, and the average annual increase was 3.18% (P < 0.001) based upon the slope of the trend test; however, the coverage increased slightly after 2010/2011. Children at high risk of influenza complications had higher influenza vaccination coverage than non at-risk children each year, and the coverage was 59.15% (55.44–62.80%) and 48.74% (47.76–49.73%) during 2015/2016 among those with and without high-risk conditions, respectively. Boys and girls had similar coverage each year and similar annual increase. While the coverage increased from 2004/2005 to 2015/2016 for all age groups, the coverage decreased with age each year (−0.64 to −1.58% per age group, P < 0.001). There was a higher coverage in Northeast than Midwest, South and West each year, and the coverage was 59.29% (56.95–61.60%), 46.66% (44.57–48.76), 45.73% (44.14–47.33) and 50.44% (48.62–52.26%) during 2015/2016, respectively. No obvious difference was found by ethnicity (Hispanic or not). However, in subgroup by race, AIAN and Asian showed higher coverage than other race groups (White, Black/African American, Multiple race), and the coverage was 61.54% (53.76–68.91%), 64.74% (60.78–68.55%), 48.16% (47.06–49.27%), 46.96% (44.24–49.70%) and 51.90% (47.92–55.86%), respectively. Administration methods included flu shot and flu nasal spray, and the percentage of flu shot ranged from 79.33 to 96.70% during the study period. Table 1 Influenza vaccination coverage (at least one dose) among children aged 6 months–17 years in the NHIS, 2004/2005 through 2015/2016 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Table 1 Influenza vaccination coverage (at least one dose) among children aged 6 months–17 years in the NHIS, 2004/2005 through 2015/2016 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Characteristics Influenza vaccination coverage (95% CI) Slope 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 N 12 278 9 585 9 170 8 623 10 951 6 671 12 485 12 822 12 530 12 991 11 945 10 720 Overall 16.70 (16.05–17.38) 20.02 (19.22–20.84) 25.21 (24.33–26.11) 29.55 (28.59–30.52) 33.89 (33.00–34.78) 39.05 (37.88–40.23) 44.75 (43.87–45.63) 44.78 (43.92–45.65) 46.06 (45.18–46.94) 48.85 (47.99–49.71) 48.95 (48.05–49.85) 49.43 (48.48–50.38) 3.18 High-risk status  High risk 30.38 (27.72–33.14) 30.96 (28.16–33.87) 37.66 (34.23–41.19) 43.97 (39.97–48.03) 47.63 (44.13–51.15) 48.77 (44.25–53.30) 53.44 (50.07–56.79) 55.57 (52.27–58.83) 56.12 (52.66–59.54) 59.48 (56.00–62.89) 59.22 (55.65–62.72) 59.15 (55.44–62.80) 2.96  Not high risk 15.40 (14.73–16.09) 18.84 (18.01–19.69) 24.26 (23.34–25.19) 28.64 (27.65–29.65) 32.94 (32.02–33.87) 38.37 (37.15–39.60) 44.09 (43.19–4.00) 43.96 (43.07–44.86) 45.35 (44.44–46.26) 48.15 (47.25–49.04) 48.24 (47.31–49.17) 48.74 (47.76–49.73) 3.22 Gender  Boys 17.14 (16.21–18.10) 20.73 (19.60–21.91) 25.63 (24.38–26.90) 30.45 (29.09–31.84) 33.95 (32.70–35.21) 39.55 (37.91–41.20) 44.70 (43.48–45.92) 44.62 (43.41–45.84) 45.85 (44.63–47.07) 49.07 (47.85–50.28) 48.51 (47.26–49.77) 49.35 (48.03–50.68) 3.10  Girls 16.57 (15.63–17.54) 19.72 (18.59–20.89) 25.48 (24.20–26.80) 29.35 (27.97–30.75) 35.36 (34.08–36.65) 41.02 (39.31–42.75) 44.79 (43.53–46.06) 44.95 (43.72–46.19) 46.28 (45.02–47.54) 48.62 (47.39–49.86) 49.42 (48.12–50.72) 49.52 (48.15–50.89) 3.19 Age (years)  <1 15.41 (12.79–18.32) 16.35 (13.44–19.61) 18.66 (15.60–22.02) 19.01 (15.53–22.88) 19.46 (16.43–22.78) 23.53 (19.32–28.16) 28.77 (25.48–32.24) 27.84 (24.52–31.36) 29.03 (25.65–32.60) 29.50 (26.23–32.93) 28.76 (25.39–32.31) 29.34 (25.76–33.13) 1.47  1 44.31 (40.69–47.98) 40.03 (36.04–44.12) 44.67 (40.47–48.92) 54.69 (50.22–59.11) 52.37 (48.52–56.19) 60.98 (56.18–65.63) 62.79 (59.26–66.23) 60.18 (56.66–63.62) 63.60 (59.96–67.13) 62.45 (58.92–65.89) 59.30 (55.45–63.08) 57.58 (53.49–61.59) 1.83  2 32.46 (29.06–36.00) 34.79 (30.81–38.94) 41.28 (37.12–45.55) 46.37 (41.91–50.87) 51.31 (47.27–55.33) 56.60 (51.39–61.71) 57.97 (54.37–61.51) 56.79 (53.17–60.34) 57.62 (53.91–61.28) 61.95 (58.23–65.56) 59.45 (55.67–63.14) 60.27 (56.19–64.25) 2.64  3 22.37 (20.19–26.79) 29.12 (25.25–33.22) 42.54 (38.34–46.82) 43.82 (39.31–48.40) 49.00 (44.94–53.08) 50.27 (45.07–55.46) 54.01 (50.39–57.59) 56.32 (52.59–60.00) 51.17 (47.35–54.98) 55.66 (51.78–59.48) 55.98 (52.15–59.76) 58.66 (54.48–62.75) 2.78  4 23.27 (20.07–26.71) 27.39 (23.41–31.66) 32.49 (28.31–36.90) 39.08 (34.67–43.62) 50.00 (45.69–54.31) 55.08 (49.74–60.35) 53.84 (50.07–57.57) 52.55 (48.79–56.29) 52.51 (48.78–56.21) 55.24 (51.49–58.95) 57.05 (52.94–61.08) 60.49 (56.34–64.54) 3.18  5 20.64 (17.53–24.03) 24.27 (20.51–28.36) 35.32 (30.92–39.92) 42.95 (38.48–47.50) 45.66 (41.57–49.78) 52.67 (47.48–57.83) 55.62 (51.76–59.44) 52.65 (48.92–56.35) 58.11 (54.21–61.95) 56.30 (52.49–60.07) 57.48 (53.51–61.39) 58.72 (54.59–62.77) 3.38  6 17.70 (14.76–20.97) 21.53 (17.99–25.41) 27.73 (23.68–32.07) 34.63 (29.89–39.60) 41.39 (37.17–45.69) 47.88 (42.56–53.23) 52.86 (48.82–56.88) 54.01 (50.00–57.97) 53.62 (49.78–57.43) 56.26 (52.48–59.99) 52.84 (48.69–56.96) 55.65 (51.48–59.76) 3.63  7 15.76 (13.00–18.85) 23.69 (20.03–27.68) 26.65 (22.64–30.97) 31.42 (27.16–35.92) 36.69 (32.78–40.74) 38.72 (33.15–44.52) 48.17 (44.20–52.16) 49.54 (45.64–53.44) 46.01 (42.14–59.93) 52.95 (49.11–56.76) 55.11 (51.21–58.97) 51.26 (47.01–55.50) 3.45  8 11.54 (9.18–14.25) 18.07 (14.71–21.82) 21.38 (17.68–25.47) 28.73 (24.56–33.20) 36.31 (32.19–40.58) 38.05 (32.86–43.46) 44.27 (40.34–48.25) 47.41 (43.53–51.31) 45.23 (41.51–49.00) 48.24 (44.26–52.24) 55.06 (50.99–59.08) 46.23 (42.09–50.42) 3.61  9 14.38 (11.74–17.35) 16.93 (13.56–20.75) 24.40 (20.52–28.61) 24.94 (20.93–29.30) 33.50 (29.74–37.42) 43.25 (37.80–48.82) 46.62 (42.54–50.73) 47.18 (43.40–50.98) 44.48 (40.57–48.44) 49.84 (45.85–53.84) 47.61 (43.71–51.53) 52.53 (48.27–56.75) 3.52  10 10.21 (7.94–12.87) 16.60 (13.41–20.20) 19.20 (5.65–23.15) 23.89 (19.92–28.22) 33.27 (29.17–37.56) 38.94 (33.85–44.21) 44.79 (40.90–48.73) 42.98 (39.24–46.79) 44.80 (40.94–48.71) 47.13 (43.42–50.87) 50.71 (46.74–54.67) 44.92 (40.64–49.26) 3.61  11 12.57 (10.16–15.33) 17.79 (14.50–21.48) 21.32 (17.64–25.37) 27.02 (22.89–31.47) 31.03 (27.23–35.03) 39.72 (34.59–45.02) 42.95 (39.09–46.87) 44.79 (40.99–48.64) 47.13 (43.17–51.12) 48.80 (44.95–52.67) 49.51 (45.48–53.55) 46.38 (42.22–50.59) 3.51  12 9.16 (7.01–11.71) 14.16 (11.15–17.64) 21.50 (17.95–25.39) 27.17 (23.11–31.54) 30.46 (26.81–34.31) 34.69 (29.66–39.99) 42.99 (39.18–46.85) 44.09 (40.33–47.90) 46.31 (42.51–50.15) 50.59 (46.97–54.21) 49.45 (45.48–53.42) 52.21 (48.09–56.31) 3.99  13 12.70 (10.31–15.41) 13.37 (10.70–16.42) 18.20 (14.88–21.91) 20.65 (17.15–24.52) 27.96 (24.35–31.79) 37.02 (32.21–42.03) 42.98 (39.27–46.75) 40.45 (36.83–44.14) 41.97 (38.34–45.66) 45.96 (42.27–49.69) 49.77 (45.82–53.71) 51.34 (47.25–55.42) 3.81  14 11.00 (8.79–13.54) 14.82 (11.93–18.10) 16.77 (13.56–20.38) 22.02 (18.48–25.90) 27.52 (24.05–31.20) 29.52 (24.95–34.41) 32.15 (28.56–35.90) 35.84 (32.26–39.54) 41.62 (38.04–45.27) 43.31 (39.74–46.93) 44.19 (40.49–47.94) 44.35 (40.37–48.39) 3.31  15 9.88 (7.84–12.24) 12.95 (10.34–15.94) 16.10 (13.15–19.41) 18.99 (15.80–22.51) 22.93 (19.84–26.26) 31.85 (27.21–36.78) 33.78 (30.39–37.29) 33.33 (29.96–36.84) 37.40 (33.90–41.00) 42.41 (39.02–45.95) 41.79 (38.17–45.48) 43.62 (39.79–47.50) 3.30  16 9.17 (7.26–11.39) 12.44 (10.02–15.21) 15.99 (13.08–19.27) 22.80 (19.38–26.51) 23.50 (20.43–26.78) 26.62 (22.58–30.98) 32.41 (29.15–35.79) 32.42 (29.20–35.78) 36.62 (33.25–40.08) 39.98 (36.67–43.35) 39.35 (35.94–42.83) 41.94 (38.31–45.65) 3.06  17 8.90 (6.96–11.16) 11.83 (9.36–14.69) 16.43 (13.60–19.58) 13.43 (10.69–16.56) 19.13 (16.34–22.17) 22.20 (18.31–26.48) 30.81 (27.66–34.10) 30.68 (27.55–33.94) 34.58 (31.17–38.11) 38.48 (35.13–41.92) 35.76 (32.40–39.23) 39.77 (36.09–43.53) 2.99 Region  Northeast 18.71 (17.04–20.48) 25.04 (22.99–27.19) 29.51 (27.26–31.84) 34.27 (31.77–36.83) 40.92 (38.63–43.25) 45.20 (42.06–48.38) 51.43 (49.15–53.70) 54.13 (51.93–56.32) 53.91 (51.65–56.16) 56.57 (54.32–58.80) 58.55 (56.25–60.83) 59.29 (56.95–61.60) 3.81   Midwest 15.28 (13.91–16.73) 18.41 (16.68–20.23) 25.84 (23.84–27.92) 29.44 (27.33–31.62) 31.02 (29.11–32.98) 40.26 (37.67–42.89) 43.36 (41.44–45.29) 43.00 (41.06–44.96) 45.10 (43.09–47.12) 49.18 (47.23–51.14) 47.27 (45.24–49.31) 46.66 (44.57–48.76) 3.13  South 17.63 (16.53–18.77) 20.29 (18.98–21.64) 24.93 (23.48–26.41) 29.16 (27.57–30.79) 34.81 (33.32–36.32) 38.91 (36.97–40.89) 43.16 (41.71–44.62) 42.81 (41.38–44.26) 43.96 (42.52–45.40) 46.77 (45.33–48.22) 47.08 (45.55–48.61) 45.73 (44.14–47.33) 2.84  West 15.56 (14.30–16.90) 17.88 (16.35–19.49) 22.94 (21.24–24.71) 27.94 (26.11–29.84) 31.38 (29.70–33.09) 36.44 (34.25–38.68) 44.20 (42.55–45.87) 43.33 (41.72–44.95) 45.21 (43.57–46.86) 47.29 (45.71–48.88) 47.40 (45.76–49.05) 50.44 (48.62–52.26) 3.29 Ethnicity  Hispanic origin 17.11 (15.90–18.37) 20.65 (19.14–22.22) 24.67 (23.07–26.32) 30.38 (28.57–32.23) 33.31 (31.71–34.94) 39.84 (37.72–41.98) 46.32 (44.72–47.93) 46.71 (45.10–48.32) 46.78 (45.15–48.41) 50.08 (48.46–51.70) 49.81 (48.12–51.50) 50.67 (48.61–52.73) 3.35  Not Hispanic origin 16.66 (15.88–17.47) 19.97 (19.02–20.94) 25.71 (24.64–26.80) 29.46 (28.32–30.62) 34.33 (33.26–35.41) 38.81 (37.40–40.24) 44.07 (43.02–45.12) 43.99 (42.97–45.02) 45.76 (44.72–46.80) 48.36 (47.33–49.38) 48.60 (47.54–49.67) 49.09 (48.02–50.16) 3.10 Race  White 16.25 (15.51–17.01) 18.94 (18.01–19.89) 24.25 (23.22–25.30) 28.80 (27.67–29.96) 32.63 (31.58–33.68) 38.33 (36.94–39.74) 44.02 (42.98–45.07) 43.45 (42.42–44.48) 45.05 (44.02–46.10) 48.31 (47.29–49.33) 48.65 (47.58–49.71) 48.16 (47.06–49.27) 3.18  Black/African American 17.47 (15.80–19.24) 21.13 (19.25–23.11) 27.22 (25.04–29.48) 29.55 (27.24–31.93) 33.91 (31.78–36.09) 37.96 (35.17–40.80) 43.14 (40.99–45.31) 44.38 (42.22–46.57) 45.20 (43.00–47.40) 46.94 (44.73–49.16) 44.56 (42.19–46.95) 46.96 (44.24–49.70) 2.84  AIAN 17.14 (10.49–25.73) 34.94 (24.80–46.19) 27.64 (19.96–36.43) 35.24 (26.16–45.17) 41.74 (32.61–51.30) 43.75 (31.37–56.72) 46.50 (38.51–54.62) 53.97 (46.58–61.23) 43.71 (35.66–52.01) 49.71 (42.03–57.40) 53.85 (46.32–61.25) 61.54 (53.76–68.91) 3.13  Asian 20.83 (16.99–25.10) 26.34 (22.61–30.33) 30.75 (26.58–35.17) 36.42 (32.27–40.72) 44.26 (40.40–48.16) 44.66 (39.79–49.61) 54.64 (51.18–58.07) 53.51 (49.98–57.01) 55.57 (52.05–59.05) 57.29 (53.77–60.75) 59.92 (56.35–63.41) 64.74 (60.78–68.55) 3.75  Multiple race 22.62 (18.44–27.24) 25.28 (20.83–30.16) 31.45 (26.38–36.86) 34.42 (29.36–39.76) 41.40 (36.91–46.00) 43.38 (37.71–49.17) 45.50 (41.46–49.58) 49.79 (46.09–53.50) 50.60 (46.73–54.46) 50.67 (46.83–54.50) 49.93 (46.09–53.77) 51.90 (47.92–55.86) 2.61 Methods  Flu shot (%) 96.70 96.63 94.71 93.95 84.92 85.82 79.66 79.26 79.33 77.94 75.64 79.79 Overall, univariate logistic analysis showed that vaccine coverage was statistically different in stratified analysis by high-risk status, age, region and race, while no significant difference was found in stratified analysis by gender and ethnicity. Findings from multivariable analysis (Table 2) showed that high-risk status and region had the greatest associations with levels of vaccine coverage while adjusting for other variables. Age was consistently associated with levels of influenza vaccine coverage across all periods. In addition, compared with the white race group, races of AIAN, Asian Black/African American and multiple race showed a higher likelihood of influenza vaccination receipt, although the differences were not significantly in several periods. Table 2 Multivariable analysis between demographics characteristics and levels of influenza vaccine coverage among children aged 6 months–17 years Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 OR, odds ratio. Table 2 Multivariable analysis between demographics characteristics and levels of influenza vaccine coverage among children aged 6 months–17 years Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 Characteristics 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011 2011/2012 2012/2013 2013/2014 2014/2015 2015/2016 OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P OR P High-risk status 2.44 <0.01 1.97 <0.01 1.90 <0.01 2.10 <0.01 1.97 <0.01 1.96 <0.01 1.54 <0.01 1.65 <0.01 1.62 <0.01 1.63 <0.01 1.68 1.64 <0.01 Gender 0.96 0.46 0.95 0.33 0.96 0.43 0.97 0.50 1.07 0.10 1.07 0.28 0.99 0.89 1.03 0.41 1.02 0.54 0.97 0.37 1.03 0.39 1.03 0.43 Age 0.91 <0.01 0.93 <0.01 0.93 <0.01 0.92 <0.01 0.93 <0.01 0.96 <0.01 0.95 <0.01 0.95 <0.01 0.96 <0.01 0.97 <0.01 0.97 <0.01 0.97 <0.01 Region  Northeast 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Midwest 0.79 0.65 <0.01 0.84 0.04 0.83 0.02 0.65 <0.01 0.71 <0.01 0.77 <0.01 0.64 <0.01 0.74 <0.01 0.76 <0.01 0.63 <0.01 0.62 <0.01  South 0.92 0.25 0.74 <0.01 0.79 <0.01 0.81 <0.01 0.79 <0.01 0.64 <0.01 0.73 <0.01 0.62 <0.01 0.70 <0.01 0.68 <0.01 0.63 <0.01 0.58 <0.01  West 0.80 <0.01 0.61 <0.01 0.69 <0.01 0.69 <0.01 0.66 <0.01 0.63 <0.01 0.72 <0.01 0.58 <0.01 0.69 <0.01 0.66 <0.01 0.60 <0.01 0.65 <0.01 Ethnicity 0.98 0.72 0.90 0.11 0.95 0.47 0.83 <0.01 0.91 0.06 0.94 0.47 0.82 <0.01 0.77 <0.01 0.79 <0.01 0.81 <0.01 0.83 <0.01 0.83 <0.01 Race  White 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00  Black/African American 1.09 0.23 1.13 0.11 1.22 <0.01 1.11 0.16 1.06 0.35 0.94 0.49 1.05 0.35 1.15 0.01 1.12 0.04 1.06 0.30 0.89 0.06 1.12 0.10  AIAN 1.16 0.60 2.56 <0.01 1.20 0.40 1.51 0.06 1.42 0.08 0.78 0.46 1.32 0.10 1.68 <0.01 1.01 <0.01 1.13 0.46 1.26 0.14 1.84 <0.01  Asian 1.43 <0.01 1.68 <0.01 1.36 <0.01 1.45 <0.01 1.57 <0.01 1.13 0.36 1.58 <0.01 1.59 <0.01 1.53 <0.01 1.49 <0.01 1.61 <0.01 1.97 <0.01  Multiple race 1.34 0.03 1.42 <0.01 1.36 0.02 1.27 0.06 1.42 <0.01 1.25 0.13 1.03 0.73 1.31 <0.01 1.26 <0.01 1.08 0.36 1.05 0.55 1.19 0.05 Family income 1.00 0.63 0.99 0.40 1.13 <0.01 1.08 <0.01 1.09 <0.01 1.16 <0.01 1.10 <0.01 1.11 <0.01 1.12 <0.01 1.11 <0.01 1.13 <0.01 1.10 <0.01 Education 1.00 0.53 1.00 0.63 1.00 0.65 1.01 0.10 1.01 0.04 0.99 0.26 1.00 0.50 0.99 0.37 1.01 0.11 1.01 0.15 1.00 0.75 1.01 0.11 OR, odds ratio. Discussion Main finding of this study Data from the NHIS showed a continuous growth in influenza vaccination coverage from 2004/2005 to 2010/2011, but the coverage increased slightly thereafter among US children aged 6 months to 17 years. No obvious difference was observed by gender and ethnicity, but at-risk children, children in Northeast and race groups of AIAN and Asian had higher influenza vaccination coverage. In addition, the influenza vaccination coverage decreased with age across each year. Multivariable analysis showed that high-risk status and region had the greatest associations with levels of vaccine coverage while adjusting for other variables. What is already known on this topic Potential explanations for the observed trend after 2010/2011 are mainly unclear. Influenza A (H1N1) and influenza A (H3N2) viruses predominated since 2007/2008 in USA, and the majority of circulating strains matched vaccine strains well.3 While pediatric hospitalizations and deaths caused by influenza vary by the predominant circulating strain and from one season to the next, the adverse events (92–171 pediatric deaths; 41.4–67 hospitalizations per 100 000 for 0–4 years old; 9.4–16.6 hospitalizations per 100 000 for 5–17 years old) were relatively stable since 2012/20 13.3 However, lowest adverse events were observed during 2011/2012 (37 pediatric deaths; 16 hospitalizations per 100 000 for 0–4 years old; 4 hospitalizations per 100 000 for 5–17 years old) while a peak was observed during 2009/2010 (288 pediatric deaths; 77.7 hospitalizations per 100 000 for 0–4 years old; 27.2 hospitalizations per 100 000 for 5–17 years old).3 Withdrawal of the live attenuated influenza vaccine recommendation was not associated with an overall change in child influenza immunization rates across seasons.9 In addition, children’s likelihood of following immunization recommendations was associated with the immunization behavior of their parents.10 Therefore, for a better understanding of our findings, it would be helpful to analysis the trend of influenza vaccination coverage in their parents in future, and encouraging parental immunization is a potential tool for increasing children’s immunization rates.10,11 The perspective, programmatic design, setting, and inclusion of herd immunity affected cost-effectiveness,5 and immunization programs using group administration are more cost-effective than programs using individual administration.5,12,13 Furthermore, common factors that influence the implementation of programs were also indentified, including program leadership and governance, organizational models and institutional relationships, workforce capacity and roles particularly concerning the school nurse, communication with parents and students.14 What this study adds Higher influenza vaccination coverage was found among high-risk children and AIAN children, probably in part because special efforts are recommended to vaccinate these children3. Boys and girls had similar influenza vaccination coverage in this analysis, which was consistent with the findings from National Immunization Survey-Flu for the 2012–13 and 2013–14 influenza seasons.15 Health-care access was found to have a robust and positive association with vaccination rates for both children and adults,16 which may partially explain the decreased trend in influenza vaccination coverage with age, because younger children tend to have more frequent visits to health-care institutions and are at increased risk of hospitalization and complication. The difference in coverage by region of residence was consistent with 2008 National Immunization Survey.17 Based on 2012 NHIS for adults, Lu et al.18 also found relatively low influenza vaccination coverage in non-Hispanic black and a relatively high coverage in non-Hispanic Asia. Furthermore, this analysis also showed that, after adjusting for other variables simultaneously, high-risk status and region had the greatest associations with levels of vaccine coverage and age was consistently associated with levels of influenza vaccine coverage across all periods. In addition, race should also contribute to the levels of influenza vaccination. Limitations of this study Strength of this study included the continuous analysis of the influenza vaccination coverage from 2004/2005 to 2010/2011, and subgroups analysis were conducted by risk status, gender, age, region of residence, race and ethnicity. The findings are also subject to limitations. First, influenza vaccination coverage was based on parental report and may be subject to recall bias. Thus analysis of provider report of influenza vaccination coverage among children should be useful in future. Second, the number of influenza vaccine doses to be administered depends on the child’s age and vaccine history. Children 6 months through 8 years of age may need two doses depending on the child’s vaccine history. Given detailed influenza vaccine history was not available, full vaccination coverage among children aged 6 months–8 years was not assessed in this analysis. However, the percentage of children aged 6 months–8 years who were fully vaccinated against influenza for 2012/2013 and 2013/2014 based on parental report in US has been reported recently with the National Immunization Survey-Flu,15 and the percentages during the 2012/2013 and 2013/2014 were 41.0 and 45.2%, respectively. In addition, among those children who required two doses, about half received at least one dose in 2012/2013 and 2013/2014, suggesting that there are barriers to receipt of the second required dose.15 Finally, the response rate declined over time from 2004/2005 to 2015/2016, and healthy user bias may be of concern. However, as described in the NHIS Description, final annual weights were considered that includes design, ratio, non-response and post-stratification adjustments for sample children, and national estimates of all sample child variables can be made using these weights. Therefore, non-response should not be a major concern for this type of analysis. Conclusions In summary, while there was a continuous growth in influenza vaccination coverage from 2004/2005 to 2010/2011, the coverage increased slightly thereafter among US children aged 6 months to 17 years. More effective influenza immunization policies and programs are warranted to achieve the Healthy People 2020 target of 70% for children 6 months to 17 years. In addition to the high-risk status, region, age and even race should be considered to further promote the coverage of influenza vaccine among children. Conflict of interest None. Acknowledgements None. Funding This work was supported by Kunshan Special Fund for Social Development and Science & Technology (No.: 001ZX07) and Suzhou ‘Kejiaoxingwei’ Youth Science Project (No.: KJXW2017073). Role of funding The sponsors have no role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. Contributors The authors’ contributions to the present study were as follows: TCW and WH contributed to data collection and did the data analyses and drafted the article. WWM and LXM revised the article. TCW and LXM are responsible for the whole work. All authors have read and approved of the final version of the article. References 1 Nair H , Brooks WA , Katz M et al. . Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis . Lancet 2011 ; 378 : 1917 – 30 . Google Scholar CrossRef Search ADS PubMed 2 Lafond KE , Nair H , Rasooly MH et al. . Global role and burden of influenza in pediatric respiratory hospitalizations, 1982–2012: a systematic analysis . PLoS Med 2016 ; 13 : e1001977 . Google Scholar CrossRef Search ADS PubMed 3 COMMITTEE ON INFECTIOUS DISEASES . Recommendations for prevention and control of influenza in children, 2017–2018 . Pediatrics 2017 ; 140 : e20172550 . CrossRef Search ADS PubMed 4 Jackson ML , Chung JR , Jackson LA et al. . Influenza vaccine effectiveness in the United States during the 2015–2016 season . N Engl J Med 2017 ; 377 : 534 – 43 . Google Scholar CrossRef Search ADS PubMed 5 Ting EEK , Sander B , Ungar WJ . Systematic review of the cost-effectiveness of influenza immunization programs . Vaccine 2017 ; 35 : 1828 – 43 . Google Scholar CrossRef Search ADS PubMed 6 Office of Disease Prevention and Health Promotion (US) . Healthy People 2020: Topics & Objectives—Immunization and Infectious Diseases [cited 2017 Nov. 16]. https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectives. 7 Brown LD , Cai TT , DasGupta A . Interval estimation for a binomial proportion . Stat Sci 2001 ; 16 : 101 – 17 . 8 Santibanez TA , Lu PJ , O’Halloran A et al. . Trends in childhood influenza vaccination coverage—U.S., 2004–2012 . Public Health Rep 2014 ; 129 : 417 – 27 . Google Scholar CrossRef Search ADS PubMed 9 Robison SG , Dunn AG , Richards DL et al. . Changes in influenza vaccination rates after withdrawal of live vaccine . Pediatrics 2017 ; 140 : e20170516 . Google Scholar CrossRef Search ADS PubMed 10 Robison SG , Osborn AW . The concordance of parent and child immunization . Pediatrics 2017 ; 139 : e20162883 . Google Scholar CrossRef Search ADS PubMed 11 Yeung MP , Lam FL , Coker R . Factors associated with the uptake of seasonal influenza vaccination in adults: a systematic review . J Public Health (Oxf) 2016 ; 38 : 746 – 53 . Google Scholar PubMed 12 Rai GK , Wood A . Effectiveness of community pharmacies in improving seasonal influenza uptake-an evaluation using the Donabedian framework . J Public Health (Oxf) 2017 : 1 – 7 . 13 Hashmi S , D’Ambrosio L , Diamond DV et al. . Preventive behaviors and perceptions of influenza vaccination among a university student population . J Public Health (Oxf) 2016 ; 38 : 739 – 45 . Google Scholar PubMed 14 Perman S , Turner S , Ramsay AI et al. . School-based vaccination programmes: a systematic review of the evidence on organisation and delivery in high income countries . BMC Public Health 2017 ; 17 : 252 . Google Scholar CrossRef Search ADS PubMed 15 Zhai Y , Santibanez TA , Kahn KE et al. . Parental-reported full influenza vaccination coverage of children in the U.S . Am J Prev Med 2017 ; 52 : e103 – 13 . Google Scholar CrossRef Search ADS PubMed 16 Chiu APY , Dushoff J , Yu D et al. . Patterns of influenza vaccination coverage in the United States from 2009 to 2015 . Int J Infect Dis 2017 ; 65 : 122 – 7 . Google Scholar CrossRef Search ADS PubMed 17 Schuller KA , Probst JC . Factors associated with influenza vaccination among US children in 2008 . J Infect Public Health 2013 ; 6 : 80 – 8 . Google Scholar CrossRef Search ADS PubMed 18 Lu PJ , O’Halloran A , Williams WW et al. . Racial and ethnic disparities in vaccination coverage among adult populations in the U.S . Vaccine 2015 ; 33 ( Suppl 4 ): D83 – 91 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Journal of Public HealthOxford University Press

Published: May 15, 2018

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