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Immunity to hepatitis B vaccine in Tanzanian under-5 children

Abstract Background: Hepatitis B vaccine was introduced in Tanzania in 2002 and is administered as DPT-hepatitis B at 4, 8 and 12 weeks of life. Aim: To determine immunity to hepatitis B virus in children under 5 years attending reproductive and child health (RCH) clinics. Methods: A cross-sectional, health facility-based study was conducted between July and December 2007 at Temeke, Amana and Mwananyamala municipal hospitals in Dar es Salaam, Tanzania. Children under 5 years who had received DPT-HB vaccine as evidenced by RCH card number 1 were included. Blood samples were collected to determine hepatitis B surface antigen (HBsAg) and antibodies to hepatitis B surface antigen (anti-HBs) and hepatitis B core antigen (Anti-HBc). An anti-HBs level of ≥10 mIU/ml is regarded as protective. Nutritional and HIV status were also determined. Results: A total of 296 children under 5 years vaccinated with DPT-HB were recruited, 153 (51.7%) of whom were male. Altogether, 205 (69.3%) children had anti-HBs levels ≥10 mIU/ml. The number of DPT-HB vaccine doses, time interval since last DPT-HB dose and HIV status were significant predictors of anti-HBs levels. Five children (1.7%) were positive for HBsAg, suggesting possible vertical transmission. No child had anti-HBc antibodies. Conclusion: More than two-thirds of children under 5 years had protective anti-HBs levels. A change in the hepatitis B immunisation schedule to include a dose immediately after birth should improve immunity.