ABSTRACT
Background: Hepatitis B virus infection is a major global health problem which is known to be the main cause of liver failure, cirrhosis, and hepatocellular carcinoma. Production of anti-HBs which is stimulated by HBV vaccine, provides protection against HBV infection. However, not all vaccinated children develop protective or durable levels of antibody against HBsAg. Therefore, testing for anti-HBs levels after HBV vaccination is important. Objective: The main objective of this study was to assess serum level of antibody against hepatitis B surface antigen among vaccinated and unvaccinated children in Harar, Eastern Ethiopia. Method: A community-based comparative cross-sectional study design was used. 540 children within the ages of 5-8 years (284 vaccinated and 256 unvaccinated) were enrolled in the study using simple random sampling in selected kebeles. Three to five milliliters of blood was collected from each study participant. Serum was separated and anti-HBsAg level was determined using ELISA. A pretested, structured questionnaire was used to collect socio-demographic and HBV associated factors exposure information of the study participants and their parents. Data entry and statistical analysis were done using SPSS statistical software version 21. Logistic regressions with 95% CI were used to identify independent predictors of anti-HBs. A p-value of less than 0.05 was considered statistically significant. Results: The overall seroprotection rate detected in this study was 95.4% among vaccinated children, whereas it was only 6.2% among unvaccinated children. 3.1% of unvaccinated children were positive for HBsAg, indicating chronic disease, whereas 1.1% of vaccinated children were HBsAg+. Anti-HBs levels declined from 414 U/ml at 5 years after vaccination to 105 U/ml after 8 years. Conclusion and Recommendation: Protective levels of anti-HBs were detected in 95.4% of vaccinated children suggesting that there is no need for a further booster dose for these children