Persistence of anti-HBs and immunologic memory in children immunized with hepatitis B vaccine

Background: We aimed to examine the persistence of anti-HBs in Bangladeshi children aged 5 and 10 years after primary vaccination, and this response to a booster dose. Methods: A total of 100 children were enrolled who were divided into two groups (A and B). Group A comprised of 50 children vaccinated 5 years ago, and group B had 50 children vaccinated 10 years ago. Hepatitis B surface antibody titer was measured, and a booster dose of the vaccine was administered to those who had anti-HBs less than 10 mlU/ml. Seventeen such children from group A and 27 from group B were vaccinated with a booster dose. After one month, 12 children from group A and 18 children from group B were retested for hepatitis B surface antibody levels. Results: After 5 and 10 years of primary vaccination, 66.0% and 46.0% children had protective antibody levels. After one month of booster dose, 91.6% children responded to the increased level of anti-HBs in group A. Among them, 66.6% showed an adequate response. In group B, 88.8% had an increased level of anti-HBs antibody where 83.3% had an adequate response. Geometric mean titre of anti-HBs antibody boosted by 35 and 75 times from pre-booster time to post-booster vaccination in group A and B, respectively. Conclusion: Children had protective levels of anti-HBs antibodies at 5 and 10 years after completion of the primary vaccinations. Anamnestic response to booster vaccination confirmed the persistence of an effective immunological memory in vaccines.