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

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. 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. 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. 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.