Nationwide representative serosurvey of third-grade school children to evaluate the hepatitis B vaccination impact in Kyrgyzstan, 2022.

Abstract

Background: Kyrgyzstan introduced universal hepatitis B childhood vaccination in 1999 to reduce the burden of hepatitis B. In 2016, aligned with the goal of controlling hepatitis B in the WHO European Region, a regional target of 0.5% was set for seroprevalence of hepatitis B surface antigen (HBsAg) among targeted birth cohorts. We conducted a representative nationwide serosurvey to assess the HBsAg prevalence among third-grade school children in Kyrgyzstan in 2022.

Methods: We sampled numbers of children proportional to the population size and stratified the sample by region and urbanization level (urban/rural). We applied multistage cluster sampling with school classes as clusters. Identified participants in the survey were tested for HBsAg, using Enzyme-linked Immunosorbent Assay (ELISA), and positive samples confirmed with neutralization tests. Data on vaccination coverage for hepatitis B birth dose (HepB BD), including timing, and three doses of hepatitis B vaccine (HepB3) were collected from medical vaccination records. We calculated crude and weighted proportions for HBsAg seroprevalence and HepB BD and HepB3 coverage.

Results: From the target sample size of 3,352 children, a total of 3,183 children (95%) participated in the survey. The majority of children were 9 or 10 years old (2,964; 93%) with almost equal numbers of girls and boys (1,606; 50% boys) and rural and urban participants (1,624; 51% urban). Five participants tested positive for HBsAg in confirmatory tests. The weighted HBsAg seroprevalence was 0.12% (95% CI 0.04-0.35%). Weighted coverage for HepB BD was 88% (95% CI 86-90%) and for HepB3 90% (95% CI 86-93%). Results from crude and weighted analysis did not differ statistically.

Conclusions: Our study demonstrates the impact of a successfully implemented hepatitis B vaccination programme in Kyrgyzstan. High hepatitis B vaccination coverage has resulted in very low HBsAg seroprevalence among vaccinated birth cohorts, paving the way towards the achievement of regional hepatitis B control targets. Maintaining high vaccination uptake plus additional measures like screening of pregnant women and treatment of those infected will be key to achieve elimination of vertical transmission of hepatitis B in Kyrgyzstan.