Long term persistence of immunity to Hepatitis B after vaccination during infancy in a country where endemicity is low

BACKGROUND: The long-term response to hepatitis B vaccination during infancy has not been fully evaluated in countries where endemicity is low. METHODS: The present study was a serological investigation of immunity to hepatitis B during adolescence. In a cohort of children who were born to hepatitis B virus carrier mothers and who were vaccinated during infancy, evidence of past or current infection and the response to a single booster dose of vaccine were analyzed. Sixty-four children whose antibody levels were measured after immunization (group 1) and 52 younger siblings who did not undergo postvaccination antibody tests (group 2) were studied. RESULTS: One child in each group showed evidence of natural infection. In group 1, 32 children (50%) had undetectable antibody to hepatitis B surface antigen (anti-HBs), and only 8 (13%) had levels >100 mIU/mL. After a booster dose of vaccine, only 7 (11%) still had undetectable anti-HBs, 3 (5%) showed a primary response, and 50 (78%) had levels >100 mIU/mL. Five of the 7 vaccine nonresponders and all of the primary responders had also received hepatitis B-specific immunoglobulin (HBIG) at birth. The children in group 2 showed a similar response to the vaccine, but with slightly higher levels of anti-HBs. CONCLUSIONS: Most children vaccinated at birth retain immunological memory to hepatitis B vaccine for 15 years, but those who did not were more likely to have received HBIG at birth, suggesting that passive antibody may interfere with the induction of immunological memory.