Hepatitis B vaccine: immune responses in children from families with an HBsAg carrier

Abstract

A 16 microgram dose of HBsAg prepared by the National Institute of Allergy and Infectious Diseases was administered to 71 children, 18 months to 16 years old. The frequency of seroconversion reached 59% (range: 50-78%) at two weeks following the first dose of vaccine and approached 100% one month after the second dose. There were virtually no side effects. Children less than three years of age developed significantly greater anti-HBs responses than did older children or adults. This appears to be related to the greater dose in microgram kg-1 administered to these children. Anti-HBs responses (mIU ml-1) to the vaccine by the Oriental participants were lower at each sampling interval. Our data suggest that prolonging the third dose of vaccine past six months (e.g. to 12 months) may not significantly alter the eventual antibody levels attained by the vaccinees, but may result in suboptimal protection between the second and third dose in some of them.