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The long-term immunogenicity of and protection provided by a plasma-derived hepatitis B vaccine was determined in a cohort of 98 susceptible Chinese neonates immunized in 1982–1983. Within 24 hours of birth, 89 infants received the first of three 30-µg doses of vaccine (at 0, 1, and 6 months) and were subsequently followed up by testing for serological markers of hepatitis B virus and by determining levels of alanine aminotransferase annually for 9 years. After the primary series of vaccine doses, 74 (83%) of 89 subjects developed antibody to hepatitis B surface antigen (anti-HBs). At the 9-year follow-up, 51% of vaccinees still had levels of antibody of 10 mIU/mL, considered the protective level. Seven responders to vaccine (9.4% of 74 evaluable patients) developed antibody to hepatitis B core antigen, and in six of these responders, levels of anti-HBs increased transiently. None of the vaccinees developed chronic carriage of hepatitis B surface antigen or clinical hepatitis. Immunization of high-risk neonates with a plasma-derived hepatitis B vaccine can induce long-lasting protective immunity that can prevent or modify primary infection for at least 9 years. Booster doses are not necessary during this period.

The long-term immunogenicity and protection provided by a plasma-derived hepatitis B vaccine was determined in a cohort of susceptible Chinese adolescents who were immunized in 1986. Ninety-fivechildren, aged 13 to 15 years, received three vaccine doses (at 0,1, and 2 months), and during subsequent annual follow-ups for 5 years, their serological markers for hepatitis B virus and levels of alanine aminotransferase were determined. After the primary vaccine series, 94 subjects (99%) developed antibody to hepatitis B surface antigen (anti-HBs). At the 60-month follow-up, 73% of vaccinees still had levels of antibody at or above 10 mIDjmL, which is considered the protective level. Nine vaccine responders (9%) developed antibody to hepatitis B core antigen, and in eight of these individuals, levels of anti-HBs increased transiently. None of the adolescents developed detectable levels of hepatitis B surface antigen or clinical hepatitis. Immunization of high-risk adolescents with a plasma-derived hepatitis B vaccine can induce long-lasting protective immunity that can prevent or modify primary infection for at least 5 years. Immunization with booster doses is not necessary during this period.