Seroprotection after hepatitis B vaccination amongst infants aged between 12 and 24 months in Ho Chi Minh City, Vietnam

Objective: To assess levels of HBsAb amongst infants who received hepatitis B vaccine in the Expanded Program on Immunization in Vietnam. Methods: A cross-sectional study was carried out at 16 community health centers from February 2016 to July 2017. Eligible infants were tested for HBsAb and HBsAg. Structured questionnaires were used to collect relevant information about the demographics of the parents/caregivers and their infants after physical examination. Results: A total of 199 eligible infants were selected with a mean age of (17.3 +/- 4.5) months. Protective antibody levels with HBsAb >= 10 mIU/mL were detected in 68.3% of infants. Of these, antibody levels :from 10 to 99 mIU/mL were 48.5% of those tested and antibody levels >= 100 mIU/mL were recorded as 51.5%. No cases were recorded of being infected with hepatitis B virus. The rate of positive HBsAb level in those who were not wasting and 18 months old was less than that among those who were <18 months old (OR 0.49, 95% CI: 0.26-0.92, P<0.05) while the infants with wasting and <18 months were less likely to be positive HBsAb than those who were not wasting and of the same age group (OR 0.15, 95% CI: 0.04-0.55, P<0.05). Conclusions: Seroprotection against hepatitis B virus was low in the infants tested (at 68.3%), which suggests that the hepatitis B vaccine should he administered with one additional close for infants between 12 and 24 months of age, particularly those with wasting.