Clinical and immunologic studies were performed in association with revaccination with live measles vaccine in 75 adolescents 11 to 14 years after immunization with killed measles vaccine. Ten subjects had local pain with swelling or erythema or both at the injection site; in three, the local reactions were severe and disturbing systemic complaints were also noted. These marked reactions were more common in subjects in whom the interval between the last dose of killed vaccine and the dose of live vaccine of the primary immunization series was less than or equal to 2 months, in subjects with prevaccination serum HAI antibody titers of less than or equal to 5, and in subjects with high measles antigen specific lymphocyte stimulation ratios. Serum complement levels could not be correlated with clinical reactions. Measles specific lymphocyte stimulation ratios were significantly higher in recipients of killed vaccine than in three compara,ive groups, in subjects with a killed-live interval in the initial vaccine series of less than or equal to 2 months as compared with greater than or equal to 3 months, and in subjects with prevaccination HAI antibody titers of less than or equal to 5 as compared with titers greater than or equal to 10. Although both low serum antibody and high measles specific lymphocyte reactivity were associated with marked local reactions, and probably indicative of susceptibility to atypical measles, our findings suggest that exaggerated lymphocyte reactivity is of greater importance in the adverse clinical response.
