The changing impact of non-pharmaceutical interventions on COVID-19 transmission across different pandemic stages in 12 Asian countries: an ecological study

Objective To investigate the impact of non-pharmaceutical interventions (NPIs) on COVID-19 transmission in different pandemic stages across 12 Asian countries. Design This was an ecological study of publicly available data.

This study used the Stringency Index from the Oxford COVID-19 Government Response Tracker (OxCGRT) as a composite measure of implementation strictness of non-pharmaceutical interventions. Setting Data were obtained from Our World in Data and OxCGRT (January 2021 to September 2022).

Participants 12 countries were included in the study: Azerbaijan, Turkey, Bahrain, Israel, Lebanon, Japan, South Korea, Singapore, Malaysia, Thailand, Cambodia, and Indonesia. Main outcome measure The instantaneous reproduction number (Rt).

Rt is defined as the expected number of secondary infections occurring at time t, divided by the number of infected individuals, each scaled by their relative infectiousness at time t (an individual's relative infectiousness is based on the generation interval and time). Results Three different pandemic development patterns were identified: Cluster 1 countries (marked by distinct fluctuation), Cluster 2 countries (characterised by smaller fluctuation) and Cluster 3 countries (featuring a peak between July and September).