This study examines the impact of mass gatherings on the local transmission of COVID-19 in Hong Kong, focusing on the period when public gathering restrictions were relaxed, coinciding with demonstrations against the National Security Law in mid-2020. Using a Synthetic Control Method (SCM), the study constructs a counterfactual scenario without mass gatherings to compare with the actual infection patterns. Results show a substantially higher infection rate in Hong Kong compared to the synthetic control, indicating that mass gatherings significantly increased COVID-19 infections. The findings highlight the importance of strict social distancing policies, especially the prohibition of large group gatherings, to prevent and control COVID-19 outbreaks.
