Spatial and Temporal Disparities in Timely Hepatitis B Birth-Dose Vaccination in Chongqing, China, 2016–2025

Background: Timely hepatitis B vaccine birth-dose (HepBV-BD) vaccination is a cornerstone strategy for preventing mother-to-child transmission of hepatitis B virus (HBV). Although hepatitis B vaccination coverage in China has improved substantially, evidence regarding long-term district-level spatiotemporal inequalities in timely birth-dose vaccination remains limited, particularly in western China. This study assessed spatiotemporal disparities in hepatitis B vaccination coverage across Chongqing, China, from 2016 to 2025. Methods: This ecological descriptive study used district- and county-level vaccination surveillance data from the Chongqing Immunization Information Management System. Temporal trends in HepBV-BD, timely birth-dose (TBD), HepBV2, and HepBV3 coverage were analyzed. Regional disparities, interregional inequalities, and spatial clustering were assessed using Global Moran’s I and Local Indicators of Spatial Association (LISA). Results: All vaccination indicators improved substantially during the study period. TBD coverage increased from 81.9% to 95.4%, whereas HepBV3 coverage increased from 83.7% to 98.7%. TBD coverage was strongly positively associated with HepBV3 coverage(r = 0.95, p < 0.001). Mountainous ethnic minority regions consistently exhibited the lowest TBD coverage despite marked improvement over time. Absolute interregional inequality decreased from 30.8 to 8.4 percentage points. Although Global Moran’s I was not statistically significant, LISA analysis identified persistent localized low-coverage clusters in southeastern mountainous regions and emerging high–high clusters in northern Chongqing. Conclusions: Hepatitis B vaccination coverage in Chongqing improved markedly between 2016 and 2025, accompanied by declining geographic inequality. Nevertheless, persistent spatial inequities in timely birth-dose vaccination remained in mountainous ethnic minority areas. Continued monitoring of spatial inequalities, together with strengthened primary healthcare capacity, culturally tailored health education, and equitable resource allocation, may help support geographically targeted immunization strategies and accelerate progress toward the WHO goal of eliminating viral hepatitis as a public health threat by 2030.