The intersection of health inequalities and COVID-19: Evidence from National Health Insurance Big Data in South Korea.

Health inequalities persist along lines of income and wealth, shaped by unequal access to healthcare, differences in health behaviors, and pre-existing chronic conditions. The COVID-19 pandemic further put families in Korea under health strain and worsened their health outcomes. This study investigates how pre-existing socioeconomic disparities intersect with health outcomes. Using the national administrative health big data provided by the Korean National Health Insurance Service, we employ logistic regression models for 10,459,043 randomly sampled cases from a total of more than 34 million registered positive cases in the country. We specifically examine whether and to what extent individuals from lower income backgrounds with positive cases are more or less likely to experience negative health outcomes. Our findings reveal that individuals from higher income backgrounds are less likely to experience negative health outcomes compared to the lowest income group, including hospitalization (odds ratio [OR] = 0.45, confidence interval [CI] = 0.44, 0.46), severe illness (OR = 0.70, CI = 0.61, 0.81), and fatalities (OR = 0.40, CI = 0.38, 0.41). Furthermore, our subsample analyses based on various demographic characteristics consistently showed that individuals from higher income backgrounds face a lower risk of adverse health outcomes. These results indicate that disadvantaged individuals are disproportionately affected by the health crisis, deepening health inequities. This paper emphasizes the need for targeted public policies.