Seroconversion following Hepatitis B immunization in National Immunization Programme in a selected Medical Officer of Health area in Galle District

Introduction: Hepatitis B immunization was introduced into the National Immunization Programme (NIP) of Sri Lanka in three phases in 2003. The study evaluates the protective efficacy of 2, 4, 6 month schedule of hepatitis B vaccination in the NIP in Sri Lanka. Methods: A cross sectional study carried out among 154 infants (completed 9 months of age) attending the NIP in the Bope Poddala Medical Officer of Health (MOH) area in Galle District in 2008. Hepatitis B surface antibody (HBsAb) titres were tested using a quantitative enzyme immunoassay test. Forty-two infants detected with low titres of antibodies were given a booster dose of hepatitis B vaccine and HBsAb titer was retested 2 - 4 weeks later. Results: The overall protection (HBsAb titre >10 mIU/mL) after 3 doses of vaccine was 94.2% with a geometric mean titre of 233.37 mIU/mL. There were 5.8% infants with HBsAb titres <10 mIU/mL and 30.5% with HBsAb titres between 10 to 100 mIU/mL. Sex, birth weight, body mass index and weight for height were not significantly associated with HBsAb levels. None of the infants had potential risk factors for acquiring hepatitis B virus infection. Only 26 out of 42 revaccinated infants returned for repeat testing of antibody levels where all had demonstrated a protective level.