Attenuated strains of the three types of poliovirus were used in a study of 550 volunteer subjects. Subjects in group A received a placebo during the first 76 days of the study while those in group B received the polioviruses by mouth; during the remaining days (78th to 139th) group A received the viruses and group 8 the placebo. No particular type of symptom or reaction marked the entrance of the virus into the body. The children, and to a lesser extent the adults, receiving the virus manifested a generally increased titer of neutralizing antibody. The results for children and adults receiving the placebo were quite different. The positive responses occurred despite the fact that a substantial number of the participants had previously received Salk vaccine. Although the effectiveness of vaccination needs to be demonstrated finally in encounters with the disease itself, this study yielded strong evidence of the effectiveness as well as the safety of the living attenuated poliovirus used.
JAMA – American Medical Association
Published: Jun 20, 1959