Serologic responses of children after primary vaccination and revaccination against smallpox

Three serologic test methods were used to study immunologic responses of 36 children vaccinated against smallpox. Following successful primary vaccination, 97 percent of the children converted for neutralizing and HI antibodies and 18 percent for CF antibodies, 3 of 33 children had a 4-fold or greater decrease for neutralizing antibodies, but 29 of 33 children had a decrease for HI antibodies. All children became negative for CF antibodies. After the second vaccination 15 months later in which only one child failed to respond clinically, 78 percent of the children had a 4-fold or greater neutralizing antibody rise; in contrast only 18 per cent showed a significant HI antibody titer increase; 44 per cent converted for CF antibodies. (AU)