Clinical and serologic study of four smallpox vaccines comparing variations of dose and route of administration. Primary percutaneous vaccination.

In an investigation of the antigenicity and reactogenicity of four smallpox vaccines, 786 children received primary percutaneous vaccination with vaccine in one of three concentrations, 10(6), 10(7), or10(8) pock-forming units/ml. Dose-response curves indicated that the three licensed vaccines (New York City Board of Health strains grown in calf lymph or chorioallantoic membrane, and the Lister vaccine) had similar potencies, but the CV-1 strain was about 10-fold less infectious. CV-1 also produced smaller skin lesions than the other three vaccines, and the incidence of fever in CV-1 vaccines who developed either "major reactions" or serum antibody was not significantly different from that in children in all vaccine groups with no evidence of "take." Hemmagglutination-inhibiting antibody was consistently seen in individuals who received potent New York City and Lister vaccines, and neutralizing antibody was induced in 82%-85% of children in this group who had some evidence of take (production of hemagglutination-inhibiting antibody or or major reaction). Only 30% of CV-1 vaccines with takes produced neutralizing antibody. Minor complications occurred in all groups, but most often in children who received the New York City strains."