Optimal Timing and Effectiveness of COVID-19 Outbreak Responses in China: A Modelling Study

Abstract

Background. In January 2020, an outbreak of atypical pneumonia caused by a novelcoronavirus, SARS-CoV-2, was reported in Wuhan, China. On Jan 23, 2020, theChinese government instituted mitigation strategies to control spread. Most modelingstudies have focused on projecting epidemiological outcomes throughout thepandemic. However, the impact and optimal timing of different mitigation approacheshave not been well-studied.Methods and Findings. We developed a mathematical model reflecting SARS-CoV-2transmission dynamics in an age-stratified population. The model simulates health andeconomic outcomes from Dec 1, 2019 through Mar 31, 2020 for cities includingWuhan, Chongqing, Beijing, and Shanghai in China. We considered differences intiming and duration of three mitigation strategies in the early phase of the epidemic:city-wide quarantine on Wuhan, travel history screening and isolation of travelers fromWuhan to other Chinese cities, and general social distancing. Our model estimated thatimplementing all three mitigation strategies one week earlier would have averted 35%of deaths in Wuhan (50% in other cities) with a 7% increase in economic impacts (16-18% in other cities). One week's delay in mitigation strategy initiation was estimated todecrease economic cost by the same amount, but with 35% more deaths in Wuhanand more than 80% more deaths in the other cities. Of the three mitigation approaches,infections and deaths increased most rapidly if initiation of social distancing wasdelayed. Furthermore, the social distancing of working-age adults was most critical toreducing COVID-19 outcomes versus social distancing among children and/or theelderly.Conclusions. Optimizing the timing of epidemic mitigation strategies is paramount andinvolves weighing trade-offs between preventing infections and deaths and incurringimmense economic impacts. City-wide quarantine was not as effective as city-widesocial distancing due to its much higher daily cost than social distancing. Under typicaleconomic evaluation standards, the optimal timing for the full set of control measureswould have been much later than Jan 23, 2020 (status quo).