Impact of the universal hepatitis B immunization program in Mongolia: achievements and challenges

Area of Science:

• Public Health
• Immunology
• Epidemiology

Background:

• The impact of Mongolia's universal infant hepatitis B (HB) immunization program, established in 1991, requires evaluation.
• Assessing the long-term effectiveness of the HB vaccination program is crucial for public health strategies.

Purpose of the Study:

• To evaluate the seroprevalence of hepatitis B virus (HBV) infection and carriage among Mongolian children.
• To determine the coverage of the infant hepatitis B vaccination program across different regions of Mongolia.

Main Methods:

• A nationwide school-based cross-sectional serosurvey was conducted in 2004.
• Stratified, multistage, random cluster sampling included 593 public elementary schools, testing 1,145 children for HBV serological markers.

Main Results:

• Complete HB vaccination coverage was 60.1%, with significant disparities: 75.2% in Metropolitan cities versus 55.7% in Province centers and 59.1% in rural areas.
• HBV infection prevalence was 5.9% in fully vaccinated urban children, rising to 20.8% in rural areas, with corresponding HB surface antigen (HBsAg) carrier rates of 1.2% and 8.6%.
• Protective anti-HBs levels were found in only 17.0% of children, decreasing with age, indicating waning immunity over time.

Conclusions:

• HBV infection and carriage rates have significantly decreased in Mongolia's younger generation compared to previous data.
• Low vaccination coverage in Province centers and rural areas highlights a need for targeted interventions to improve HB immunization access and uptake.