Impact assessment of the national immunization program against hepatitis B in Mongolia

Introduction: Universal hepatitis B immunization is the most effective means for prevention of HBV infection worldwide. Since 1991, hepatitis B vaccination has been an integral part of Mongolia's Expanded Program of Immunization. We aimed to assess the impact of vaccination program after more than 10 years of its implementation. Methods: A representative, population based nationwide cross-sectional study was implemented in 2009-2010. Tests for HBsAg were performed using rapid test from Abbott, Japan. Results: A total of 5894 children were participated in the survey out of 6380 selected (response rate 92.38%) children (2839 girls) who were aged 4-6 years. Prevalence of HBsAg carriage was 0.53% without significant differences by age and sex. The HBsAg-positivity rate in Metropolitan cities, rural province center, and villages were 0.33%, 0.34%, and 0.77% respectively. Nearly 99% of children received at least one dose of hepatitis B or pentavaccine whereas 81.9% were fully and 16.7% were partially vaccinated. Around 95% of the children were received the first dose of hepatitis B vaccine, of whom 3413 (76.5%) received within 24 hours while 1274 (27.8%) had received later than the schedule. Prevalence of HBsAg carriage among fully and partially vaccinated children was 0.55% and 0.61%, respectively. Administration time of the first dose of hepatitis B vaccine was significantly correlted with the prevalence of HBV carriage among children (p=0.016). Conclusions: National vaccination program against hepatitis B successfully decreased the prevalence of HBV carriage among children. Vaccination coverage of hepatitis B vaccine is high, however first dose need to be administered timely.