Prevalence of hepatitis B surface antigen in vaccinated children and controls in rural Nigeria.

Summary Objective: To determine the prevalence of hepatitis B surface antigen (HBsAg) amongst vaccinated children and controls aged 1–4 years in a rural community in mid-western Nigeria. Methods: The vaccinated children had received at least three doses of hepatitis B vaccine. The vaccines included recombinant hepatitis B vaccine at birth and a combined diphtheria, tetanus, pertussis (whole cell) plus hepatitis B (DTPw-HBV) vaccine. HBsAg was determined by a rapid immunoassay method based on the immunochromatographic sandwich principle. Two hundred and twenty-three children and 219 controls were recruited into the study. Results: The prevalence of HBsAg was significantly lower in the vaccinated group (1.3%) than in the control group (4.6%, p =0.04). The prevalence rates were significantly higher in males ( p =0.02) and two-year birth cohort ( p =0.01). The controls were estimated to be at a six-fold higher risk of being positive for the surface antigen than the vaccinated children. The vaccine effectiveness was estimated to be approximately 80%. Conclusion: These results confirm that hepatitis B vaccine protects against hepatitis B surface antigen carriage and confirm immunogenicity of the combined DTPw-HBV vaccine.