Passive-active immunisation against hepatitis B: immunogenicity studies in adult Americans.

Three sex and age matched groups of medical personnel, 20-40 individuals in each, received a course of hepatitis B vaccine: in one group the first dose of vaccine was given a month after injection of hepatitis B immune globulin; in the second, vaccine and immune globulin were given simultaneously; and, in the third, vaccine was given alone. The passively acquired antibody did not interfere with an active immune response to the vaccine. Both the timing of antibody appearance and the antibody titres were similar in the three groups, and the actively acquired antibody persisted for the 8 months of follow-up. Administration of the vaccine together with hepatitis B immune globulin will provide immediate protection, whereas people who receive vaccine alone may lack antibody for several months. This opens new possibilities for post-exposure prophylaxis.