Geospatial disparities in post-pandemic SARS-CoV-2 vaccination: Evidence from Chile beyond the national success

While Chile achieved one of the world's highest and most equitable SARS-CoV-2 vaccination coverages during the pandemic, less is known about the post-pandemic stage. This study examines within-country geospatial disparities in COVID-19 vaccination uptake and their socio-demographic determinants in two urban areas of Chile. A population-based survey conducted in May 2024 collected individual data on vaccination status and socio-demographic characteristics. These were georeferenced and linked to census information at the household block level. Spatial analyses explored clustering and correlations between the number of vaccine doses and variables such as age structure, educational attainment, overcrowding, and proximity to public health facilities. Moran's Index was used to assess spatial autocorrelation and bivariate relationships, disaggregated by sex and city. The number of vaccine doses inoculated displayed significant spatial concentration, particularly among women. A positive spatial correlation was found between vaccination and higher education, and a negative correlation with overcrowding in one city. Distance to health facilities was not significantly associated with vaccine uptake. Across both cities, a higher proportion of older adults was associated with higher vaccination rates, with gender-specific patterns observed. Despite Chile's previously homogeneous vaccination performance, post-pandemic findings reveal emerging socio-spatial disparities. The return of demographic and territorial determinants suggests a shift toward structural influences on vaccine uptake. These results underscore the need for territorially tailored public health strategies to reduce intra-country disparities in immunization access over time.