Background: The COVID-19 outbreaks associated with mass religious gatherings which have the potential of invoking epidemics at large scale have been a great concern. This study aimed to evaluate the risk of outbreak in mass religious gathering and further to assess the preparedness of non-pharmaceutical interventions (NPIs) for preventing COVID-19 outbreak in this context. Methods: The risk of COVID-19 outbreak in mass religious gathering was evaluated by using secondary COVID-19 cases and reproductive numbers. The preparedness of a series of NPIs for preventing COVID-19 outbreak in mass religious gathering was then assessed by using a density-dependent model. This approach was first illustrated by the Mazu Pilgrimage in Taiwan and validated by using the COVID-19 outbreak in the Shincheonji Church of Jesus (SCJ) religious gathering in South Korea. Results: Through the strict implementation of 80% NPIs in the Mazu Pilgrimage, the number of secondary cases can be substantially reduced from 1508 (95% CI: 900–2176) to 294 (95% CI: 169–420) with the reproductive number (R) significantly below one (0.54, 95% CI: 0.31–0.78), indicating an effective containment of outbreak. The expected number of secondary COVID-19 cases in the SCJ gathering was estimated as 232 (basic reproductive number (R0) = 6.02) and 579 (R0 = 2.50) for the first and second outbreak, respectively, with a total expected cases (833) close to the observed data on high infection of COVID-19 cases (887, R0 = 3.00). Conclusion: We provided the evidence on the preparedness of NPIs for preventing COVID-19 outbreak in the context of mass religious gathering by using a density-dependent model.
- Mass gathering
- Non-pharmaceutical intervention
- Religious activity