PEDIATRIC EXPERIENCE WITH RECOMBINANT HEPATITIS-B VACCINES AND RELEVANT SAFETY AND IMMUNOGENICITY STUDIES

Yeast-derived recombinant hepatitis B vaccines have replaced plasma-derived vaccines in the United States and have now been given to millions of infants and children throughout the world. Routine immunization of infants in the United States with hepatitis B vaccine has been endorsed as the optimal means to prevent infection. The recombinant vaccines have an excellent safety record; most children have no adverse reactions whereas a few experience only minor local and systemic reactions that resolve within a short time. Both of the vaccines licensed in the United States are highly immunogenic in infants and children who complete a three dose vaccination sequence. Approximately 95 to 100% achieve protective levels of antibody to hepatitis B surface antigen (greater-than-or-equal-to 10 mIU/ml) after three doses. Immunization may begin at birth or at 1 to 2 months of age, and hepatitis B vaccine may be given simultaneously with other routine childhood vaccines. Antibody levels to hepatitis B surface antigen gradually wane over time, and the duration of maintaining protective levels correlates strongly with the peak level achieved. The protective efficacy against perinatal transmission from mothers who are positive for hepatitis B surface antigen and e antigen is 90 to 100% when the first dose of vaccine is administered at birth with hepatitis B immunoglobulin. In highly endemic populations immunization in infancy also protects against horizontal transmission from chronically infected family members. Studies currently in progress will determine the duration of protection, the potential need for booster doses and the feasibility of combining antigens in multivalent vaccines.