LONG-TERM EFFICACY OF ACTIVE POSTEXPOSURE IMMUNIZATION OF INFANTS FORPREVENTION OF HEPATITIS-B VIRUS-INFECTION

Perinatal transmission of hepatitis B virus (HBV) contributes to the h igh prevalence of chronic infection in China and many other countries. In a placebo-controlled trial among 166 infants, the 12-month efficac y of active postexposure prophylaxis to prevent chronic perinatal HBV infection varied by vaccine (range, 45%-89%). In a 5-year follow-up st udy, 2 additional infants became chronically infected with HBV, and th e efficacy of active prophylaxis was estimated to be 38% and 72% for t he two vaccines at 5 years. In addition, 80% of immunized infants cont inued to have protective levels of antibody at the end of 5 years. How ever, among 27 infants who received passive-active immunoprophylaxis w ith high-dose hepatitis B immune globulin, only 60% (11/19) had protec tive antibody levels. These data indicate that active postexposure imm unization initiated soon after birth continues to provide protection d uring early childhood when there is a high risk of chronic HBV infecti on.