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

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.