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 (HB(s)Ag) and antibodies to hepatitis B surface antigen (anti-HB(s)) and hepatitis B core antigen (Anti-HB(c)). An anti-HB(s) level of > or =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-HB(s) levels > or =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-HB(s) levels. Five children (1.7%) were positive for HB(s)Ag, suggesting possible vertical transmission. No child had anti-HB(c) antibodies.

Conclusion: More than two-thirds of children under 5 years had protective anti-HB(s) levels. A change in the hepatitis B immunisation schedule to include a dose immediately after birth should improve immunity.