Nationwide Results of COVID-19 Contact Tracing in South Korea: Individual Participant Data From an Epidemiological Survey (Preprint)

Abstract

BACKGROUND Evidence regarding the effectiveness of contact tracing of coronavirus disease 2019 (COVID-19) and the related social distancing is limited and inconclusive. OBJECTIVE To investigate the epidemiological characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in South Korea and evaluate whether a social distancing campaign is effective in mitigating the spread of COVID-19. METHODS We used contract tracing data to investigate the epidemic characteristics of transmission of SARS-CoV-2 in South Korea and evaluate whether a social distancing campaign is effective to mitigate the spread of COVID-19. We calculated the mortality rate for COVID-19 by infection type (cluster versus non-cluster) and tested whether new confirmed COVID-19 trends changed after a social distancing campaign. RESULTS There were 2537 patients with confirmed COVID-19 who completed the epidemiologic survey: 1305 (51.4%) cluster cases and 1232 (48.6%) non-cluster cases. The mortality rate was significantly higher in cluster cases linked to medical facilities (0.41% versus 7.70%; adjusted percentage difference, 7.99%; 95% confidence interval [CI], 5.83 to 10.14) and long-term care facilities (0.41% versus 8.60%; adjusted percentage difference, 7.56%; 95% CI, 5.66 to 9.47) than in non-cluster cases. The change in trends of newly confirmed COVID-19 cases before and after the social distancing campaign was significantly negative in the entire cohort (adjusted trend difference, -2.28; 95% CI, -3.88 to -0.68) and the cluster infection group (adjusted trend difference, -0.96; 95% CI, -1.83 to -0.09). CONCLUSIONS In a nationwide contact tracing study in South Korea, COVID-19 linked to medical and long-term care facilities significantly increased the risk of mortality compared to non-cluster COVID-19. A social distancing campaign decreased the spread of COVID-19 in South Korea and differentially affected cluster infections of SARS-CoV-2. CLINICALTRIAL N/ACOVID-19; contact tracing; coronavirus.