title: Impact of the universal hepatitis B immunization program in Mongolia: achievements and challenges.
abstract: 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.
authors.affiliation: Department of Public Health, Jichi Medical University School of Medicine, Shimotsuke, Tochigi, Japan. davaamon@jichi.ac.jp
authors.forename: Dambadarjaa
authors.initials: D
authors.lastname: Davaalkham
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ojima
authors.forename: Ritei
authors.initials: R
authors.lastname: Uehara
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.forename: Izumi
authors.initials: I
authors.lastname: Oki
authors.forename: Steven
authors.initials: S
authors.lastname: Wiersma
authors.forename: Pagvajav
authors.initials: P
authors.lastname: Nymadawa
authors.forename: Yosikazu
authors.initials: Y
authors.lastname: Nakamura
mesh_terms: D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D017325:Hepatitis B Vaccines / Q000008:administration & dosage*; D006801:Humans; D017589:Immunization Programs / Q000458:organization & administration*; D008297:Male; D008986:Mongolia / Q000453:epidemiology; D009313:National Health Programs / Q000458:organization & administration*; D015397:Program Evaluation; D016036:Seroepidemiologic Studies
chemical_list: D017325:Hepatitis B Vaccines