HBsAg prevalence among children under 5 years

The purpose is to describe the reduction in chronic hepatitis B virus (HBV) infection among children, towards the 2030 hepatitis elimination goals. Most HBV-related morbidity and mortality result from infections acquired early in life. Consequently, prevention efforts focus on children under 5 years of age. HBsAg prevalence among children serves as a proxy measure of chronic HBV infection and progress towards hepatitis elimination.

Proportion of children under 5 years of age who test positive for hepatitis B surface antigen (HBsAg), indicating chronic HBV infection. HBsAg is a protein from the virus coat and its presence indicates active HBV infection.

Chronic hepatitis B infection; HBV infection; hepatitis B surface antigen (HBsAg); childhood HBV transmission

Depending on data availability and survey design: sex, place of residence, exposure to HepB birth dose vaccination, exposure to HepB3 vaccination, and geographic level.

HBsAg prevalence is measured through population-based serosurveys using laboratory testing of blood specimens. Numerator: number of children with a positive HBsAg test. Denominator: number of children tested with a valid HBsAg result. Estimates may be adjusted for survey design

Country estimates are derived from serological survey data and other available epidemiological evidence using mathematical modelling. Inputs include HBsAg prevalence data, vaccination coverage, demographic data, and HBV transmission parameters

HBV model structure (PRoGReSs model): the HBV model uses a dynamic mathematical framework that estimates annual HBV prevalence and incidence by stage of liver disease, age and sex using disease progression and mortality (all-cause and liver-related) rates. The model integrates demographic profiles, vaccination coverage (including timely birth dose and three-dose infant series), prevention measures such as hepatitis B immune globulin (HBIG) and maternal antiviral prophylaxis, HBV diagnosis and treatment schedules, and established HBV epidemiological parameters. Perinatal, early childhood and horizontal transmission are modelled using age-specific hepatitis B surface antigen (HBsAg) prevalence together with available prevention-coverage data. This allows the model to reflect both historical and current programme performance.

Regional and global estimates are produced by aggregating country estimates generated through standardized modelling approaches using available epidemiological and demographic data.

100

Every two years

Continuous collection as new serosurvey and programmatic data become available; model inputs are typically updated biennially.

Comparability and Interpretation: This indicator serves as a standardized proxy measure of chronic HBV infection in early childhood and is appropriate for monitoring global progress toward elimination goals. National validation and programme assessment should consider country-specific epidemiological data and serological survey evidence.

This dataset contains a combination of country-reported data and WHO-supported modelled estimates. Values may differ because they are derived from different data sources, population coverage, reference years and methodologies. Country-reported data are intended primarily for national programme monitoring, whereas modelled estimates are intended to support standardized comparisons across countries and over time. Direct comparisons between country-reported and modelled values, or between countries represented by different observation types, should therefore be made with caution. Differences between WHO estimates and official national figures should not necessarily be interpreted as errors but may reflect methodological and data-source differences.

hepatitisreporting@who.int

Diana Faini

4985

Availability of direct seroprevalence data among children under five is limited in many settings. Estimates rely partly on modelling and may differ from national estimates because of differences in data sources, assumptions, and population coverage. Uncertainty is greater where data are sparse.