doi: 10.1056/NEJMc2303518pmid: 37256992
To the Editor: Castilla et al. (Feb. 2 issue)1 evaluated the effectiveness of an unfunded meningococcal B vaccine (4CMenB) in Spain. The authors note that a potential bias in the study was that higher socioeconomic status may be associated with increased vaccine coverage (since patients have to pay for the vaccine themselves) and a lower incidence of meningococcal disease. In fact, with the use of the Valencia Health System Integrated Database,2 we found that children who had not received 4CMenB had a higher risk of social exclusion than children who had received the vaccine (13.0% vs. 4.3% were classified as . . .