Substantial decline in hepatitis B virus infections following vaccine introduction in Tajikistan
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Substantial decline in hepatitis B virus infections following vaccine introduction in Tajikistan

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    Background Tajikistan, considered highly endemic area for hepatitis B virus (HBV) in a pre-vaccine era, introduced hepatitis B vaccine in 2002 and reported ≥80% coverage with three doses of hepatitis B vaccine (HepB3) since 2004. However, the impact of vaccine introduction has not been assessed. Methods We tested residual serum specimens from a 2010 national serosurvey for vaccine-preventable diseases in Tajikistan and assessed the prevalence of HBV infection across groups defined based on the birth cohorts’ routine infant hepatitis B vaccination program implementation and HepB3 coverage achieved (≥80% versus <80%). Serosurvey participants were selected through stratified multi-stage cluster sampling among residents of all regions of Tajikistan aged 1–24 years. All specimens were tested for antibodies against HBV core antigen (anti-HBc) and those found positive were tested for HBV surface antigen (HBsAg). Seroprevalence and 95% confidence intervals were calculated and compared across subgroups using Satterthwaite-adjusted chi-square tests, accounting for the survey design and sampling weights. Results A total of 2188 samples were tested. Prevalence of HBV infection markers was lowest among cohorts with ≥80% HepB3 coverage (ages, 1–6 years): 2.1% (95% confidence interval, 1.1–4.3%) for anti-HBc, 0.4% (0.1–1.3%) for HBsAg, followed by 7.2% (4.1–12.4%) for anti-HBc and 2.1% (0.7–6.1%) for HBsAg among cohorts with <80% HepB3 coverage (ages, 7–8 years), by 12.0% (8.7–16.3%) for anti-HBc and 3.5% (2.2–5.6%) for HBsAg among children’s cohorts not targeted for vaccination (ages, 9–14 years), and 28.9% (24.5–33.8%) for anti-HBc and 6.8% (4.5–10.1%) for HBsAg among unvaccinated adult cohorts (ages, 15–24 years). Differences across groups were significant (p < 0.001, chi-square) for both markers. Conclusions The present study demonstrates substantial impact of hepatitis B vaccine introduction on reducing HBV infections in Tajikistan. To achieve further progress in hepatitis B control, Tajikistan should maintain high routine coverage with hepatitis B vaccine, including birth dose.
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