Spatial inequities in childhood vaccination coverage in South Korea: A nationwide spatiotemporal analysis, 2017-2023

This study aimed to identify clusters of undervaccination and regional determinants in South Korea.

We conducted an ecological spatiotemporal study of complete vaccination coverage among 3- and 6-year-olds in all 250 municipalities from 2017 to 2023. Global Moran's I and Getis-Ord Gi* detected spatial autocorrelation and local hotspots with low coverage. Bayesian spatiotemporal models examined associations between municipal coverage and area-level variables.

Distinct geographical inequities in childhood vaccination were identified: from 2017 to 2022, low coverage for 3-year-olds clustered in parts of Seoul and southwestern regions, while hotspots for 6-year-olds were concentrated in the southwest and parts of Seoul during 2018-2020 and shifted across regions from 2021 to 2023. In Bayesian spatiotemporal models, municipalities with higher National Health Insurance premiums and a greater share of traditional Korean medicine institutions were associated with lower complete vaccination coverage.

Even in a high-coverage and high-income setting, this study found significant spatial inequities in childhood vaccination. Regional pockets with low coverage are associated with complex socioeconomic and healthcare contexts. Thus, a universal vaccination strategy can overlook important local vulnerabilities. These findings highlight the need for targeted local interventions and sustained monitoring to ensure equitable vaccination coverage.