Examining spatial disparities in essential primary care services across multiple geographic scales in South Korea

South Korea's healthcare system exhibits significant spatial disparities in service provision, which were further exposed during the COVID-19 pandemic, particularly in Essential Primary Care Services (EPS). This study examines the spatio-temporal dynamics of these disparities through three questions: (1) How did COVID-19 influence spatial and temporal discrepancies in EPS? (2) How do these discrepancies vary across geographic scales? and (3) What spatial-health policy implications emerge, especially relative to traditional arguments about healthcare disparities in South Korea? The analysis focuses on the interaction between temporal phases (pre-, mid-, and post-pandemic) and spatial dimensions (areas and regions) to assess the pandemic's impact on EPS. To address these issues, the study introduces the Discrepancy Index (DISC) to measure spatial mismatches between EPS supply and demand, and the Disparity of Service Stress Index (DISTRES) to assess capacity mismatches in service provision. By integrating these measures across three pandemic phases and multiple geographic scales, the study provides a comprehensive assessment of spatio-temporal disparities in EPS. The findings yield several key insights. The impact of COVID-19 on EPS is not strongly evident at the national aggregate level but emerges more clearly at specific geographic scales, with several outlier units showing pronounced effects that were not captured in previous work from South Korea or other countries. Spatial disparities and their mitigation also vary by spatial units, indicating that public health policies should be tailored to the spatial units where DISC and DISTRES identify critical spatial or capacity mismatches. Spatial-temporal disparities in EPS are particularly marked between metropolitan and non-metropolitan regions and between large cities and rural areas. The standardized framework developed in this study offers an effective approach for analyzing and classifying healthcare service distributions across multiple spatial and temporal dimensions, providing deeper insight into patterns of healthcare disparity and informing scale-sensitive policy responses.