Crowded Spaces, Contagious Risks: Comparing COVID-19 Incidence After Outdoor Concerts Among University Members and the Community, Republic of Korea, 2022

BACKGROUND: A university festival, including outdoor concerts, was held from May 2 to 4, 2022, following the relaxation of coronavirus disease 2019 (COVID-19) restrictions in Korea. This study aimed to assess its impact on COVID-19 cases among university members. METHODS: We collected daily COVID-19 case data from university and local government websites and conducted a causal impact analysis using a Bayesian structural time series model. RESULTS: The analysis revealed a significant increase in cases following the event. From May 6 to 29, 2022, the university recorded an average of 5.8 daily cases (total: 138 cases). In the counterfactual scenario without the event, the estimated number of daily cases was 2.5 to 3.0 (total: 57.1 to 72.0 cases) based on three prediction models. The outdoor concerts were associated with an approximately twofold increase in COVID-19 cases among university members. CONCLUSION: Despite a declining trend in community cases, these findings underscore the potential risks of crowded outdoor gatherings in spreading COVID-19 and highlight the need for caution at such events.