Assessment of Immunity against Hepatitis B Virus among Children Aged 2-17 Years in Nnewi, Anambra State, South-East Nigeria: A Pilot Study

Background: Nigeria is one of the hyper-endemic countries for hepatitis B with national prevalence rate of 11%. No study has been done in Nigeria to the best of authors’ knowledge to assess the level of immunity among children vaccinated against HBV. Objective: To assess prevalence of Hepatitis B surface antigen, determine the presence of antibodies to hepatitis B surface antigen (anti-HBs) and determine the titre levels of anti-HBs among those who have anti-HBs. Design: This was a pilot and a cross-sectional study. Methods: Consecutive children aged between 2 and 17 years seen at the outpatient clinic of NAUTH, Nnewi, Nigeria were recruited. Questionnaire was interviewer-administered. Venous blood was collected from each participant, analyzed for HBV serological markers and anti-HBs titre. Results: A total of sixty children were recruited. There was equal male and female distribution. 36.7% were aged 10-14 years. One child did not receive HBV vaccine. There was no incidental finding of HbsAg positivity. 15% of respondents had their immunity assessed after completing vaccination. There was presence of antibodies to HBsAg in19 children, and the anti-HBs titre was protective in 78.9% of those who had antibodies. Conclusion: After 18 years of introduction of the HBV vaccine into the NPI and routine infant immunization against hepatitis B virus in Nigeria, this pilot study has shown immunity against hepatitis B is not usually assessed after immunization and a significant proportion of children who were adequately immunized are not adequately protected against HBV. A large-scale study would be desirable for confirmation.