Nationwide results of COVID-19 contact tracing in South Korea: Individual participant data from an epidemiological survey (Preprint)

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