Factors Associated with Incidence, Mortality, and Case Fatality of COVID-19: A Natural Experimental Study in South Korea

Abstract

Background: During the COVID-19 pandemic, South Korea has achieved a temporary, but nearly perfect universal health coverage model, in terms of the extent of patients and services covered by insurance. The current study investigated whether socioeconomic disparities remained in COVID-19 health outcomes under universal health coverage and sought to determine which factor exerted the greatest effect on disparities in COVID-19 outcomes.Methods: This retrospective, observational study included all 7,590 confirmed COVID-19 patients who tested positive in South Korea through May 15, 2020. We used the official medical database, released from the Ministry of Health and Welfare and Health Insurance Review and Assessment Service in South Korea. Socioeconomic status was estimated by insurance type (National Health Insurance Service [NHIS] beneficiaries and Medical Aid [MA] recipients). Incidence (per 1,000,000), mortality rate (per 1,000,000), and case fatality rate were calculated. To determine the factors associated with incidence and case fatality ratio, multivariable logistic regressions were performed at the national and regional levels.Findings: Nationwide, incidence of COVID-19 was 144·4 per 1,000,000, mortality rate was 4·3 per 1,000,000, and case fatality ratio was 3·0%. MA recipients had higher incidence (424·3 vs 136.3), mortality rate (28·3 vs 3·6), and case fatality ratio (6·7 vs 2·7) than NHIS beneficiaries. After adjustment, older age, male sex, hypertension, higher Charlson comorbidity index score, and region were associated with higher odds of COVID-19 case fatality.Interpretation: We found socioeconomic disparities in COVID-19 related health outcomes in incidence and fatality, despite universal health coverage. However, these disparities were not due to socioeconomic status in and of itself, but rather based on the poor underlying health conditions of the vulnerable.Funding Statement: This research did not receive any funding from agencies in the public, commercial, or not-for-profit sectors.Declaration of Interests: The authors declare that there are no conflicts of interests.Ethics Approval Statement: The Institutional Review Board of the Seoul Metropolitan Government, Seoul National University, Boramae Medical Center (No. 20200403/07-2020-12/043) approved this study.