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. Bangabandhu Sheikh Mujib Medical University Journal 2023;16(2): 101-105