Act Early to Prevent Infections and Save Lives: Causal Impact of Diagnostic Efficiency on the COVID-19 Pandemic

This paper examines the causal impact of diagnostic efficiency on the COVID-19 pandemic in China. Using an instrumental variable approach, we show that a 1-day decrease in the time taken to confirm the first case in a city publicly led to 9.4% and 12.7% reductions in COVID-19 prevalence and mortality over the subsequent six months, respectively. The impact was larger for cities that are farther from the COVID-19 epicenter, are exposed to less migration, have more responsive public health systems, and have higher-capacity utilization of health systems. Social distancing and a less burdened health system are likely underlying mechanisms.