BACKGROUND: The impact of the universal infant hepatitis B (HB) immunization program initiated in
1991 in Mongolia is still unclear.
METHODS: A nationwide school-based cross-sectional serosurvey was conducted in 2004, with stratified,
multistage, random cluster sampling from all public elementary schools (n=593) in Mongolia. All
children were tested for serological markers of hepatitis B virus (HBV).
RESULTS: Serology results were available for 1,145 children (592 boys and 553 girls) aged 7-12 years
(survey response rate: 93%). Immunization card was available for 702 (61.3%) children. The coverage
of complete HB vaccination was 60.1% and it was increased by birth cohort from 44% to 76%.
Significantly higher proportion of children in Metropolitan cities (75.2%) was completely vaccinated with
HB compared to those in Province centers (55.7%) and rural areas (59.1%). HBV infection occurred in
5.9%, 13.2%, and 20.8% of complete vaccinees living in Metropolitan, Province centers, and rural
areas, respectively; of whom 1.2%, 2.9%, and 8.6% were HB surface antigen (HBsAg) carriers, respectively.
Only 17.0% of the children had protective anti-HBs which decreased from 31.1% to 16.3%
among 7 to 12-year-olds indicating its decay with time.
CONCLUSIONS: Prevalence of HBV infection and carriage among young generation meaningfully
declined compared with those of previous studies in Mongolia. The coverage of birth dose and complete
HB vaccination was significantly low in Province centers and rural areas which should be taken
into consideration