The control of hepatitis B virus infection with vaccine in Japanese nursery schools.

In 1983, the efficacy of an inactivated hepatitis B vaccine was assessed among children in nursery schools in which there was at least one hepatitis B surface antigen-positive child with hepatitis B e antigen. Of the 496 children who completed the protocol, 243 (aged 2.7 +/- 1.1 years) in six of the nursery schools received three injections of the vaccine. In five other nursery schools, 253 children (aged 2.3 +/- 1.0 years) did not receive the vaccine and were used as the control group. No side effects resulted from vaccination. Two doses of the vaccine induced antibodies in 70.8% of the vaccinated children. A booster dose six months after the first induced antibodies in 82.3% of the recipients and markedly increased the proportion of recipients who produced high antibody titiers. Although nine (4.4%) of the 203 children in the control group (whom the authors were able to follow for 24 months) were infected with hepatitis B virus and two of them became carriers, none of the vaccine recipients were infected. The vaccine appears to be safe, immunogenic, and efficacious in preventing infection with hepatitis B virus in nursery schools.