Serological epidemiology of hepatitis B virus and vaccine-induced immune dynamics in 58,169 children in Wuhan, China (2019-2025): a cross-sectional analysis of waning immunity and adolescent susceptibility.

OBJECTIVES

Despite the success of the Expanded Program on Immunization (EPI) in reducing hepatitis B virus (HBV) prevalence, the long-term durability of vaccine-induced immunity and the precise trajectory of antibody decay in Chinese pediatric populations remain under-characterized. This study investigated the seroprevalence of hepatitis B surface antigen (HBsAg) and the kinetics of hepatitis B surface antibody (anti-HBs) in a large cohort of children in Wuhan to inform prime-boost vaccination strategies.

METHODS

We conducted a single-center, cross-sectional retrospective analysis of 58,169 children aged 0-17 years evaluated at Renmin Hospital of Wuhan University between January 2019 and November 2025. Serum HBsAg and anti-HBs levels were qualitative/quantified using chemiluminescence immunoassays (CLIA). Data were stratified by age, gender, and year. Statistical analyses utilized the Chi-square test for categorical variables and the Kruskal-Wallis test with Bonferroni‑corrected post-hoc pairwise comparisons for continuous variables.

RESULTS

The overall HBsAg seroprevalence was 1.27% (723/56,956). However, this rate was heavily skewed by a high frequency of transient HBsAg reactivity in neonates aged 1-30 days (11.97%), likely attributable to vaccine-induced antigenemia and assay interference. After excluding infants < 1 year, the adjusted HBsAg prevalence was 0.47%, which declined significantly from 2019 (0.81%) to 2023 (0.27%). A secondary peak in HBsAg prevalence (1.16%) was observed in adolescents aged 13 years. Among 57,004 subjects assessed for immunity, 66.27% were seroprotected (anti-HBs ≥ 10 mIU/mL). Anti-HBs seropositivity peaked at 92.64% in infants aged 7-12 months but declined precipitously to 48.98% by age 3 years. From age 5 to 17 years, protective antibody rates stabilized at suboptimal levels (30-40%). While males exhibited a higher overall response rate than females (67.21% vs. 65.03%; P < 0.001), median titers in responders did not differ by sex.

CONCLUSIONS

Although the HBsAg prevalence in Wuhan's pediatric population has decreased, the persistence of a 0.47% prevalence in children > 1 year and a resurgence of infection in early adolescence highlight gaps in the current elimination strategy. The rapid decay of anti-HBs titers by age 3 and the "juvenile pause" in immune surveillance suggest critical windows of vulnerability. These findings support the implementation of serological monitoring and targeted booster vaccination at ages 2-3 and 12-13 years to sustain population-level immunity and achieve the WHO 2030 elimination targets.