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 novel
coronavirus, SARS-CoV-2, was reported in Wuhan, China. On Jan 23, 2020, the
Chinese government instituted mitigation strategies to control spread. Most modeling
studies have focused on projecting epidemiological outcomes throughout the
pandemic. However, the impact and optimal timing of different mitigation approaches
have not been well-studied.

Methods and Findings. We developed a mathematical model reflecting SARS-CoV-2
transmission dynamics in an age-stratified population. The model simulates health and
economic outcomes from Dec 1, 2019 through Mar 31, 2020 for cities including
Wuhan, Chongqing, Beijing, and Shanghai in China. We considered differences in
timing 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 from
Wuhan to other Chinese cities, and general social distancing. Our model estimated that
implementing 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 to
decrease economic cost by the same amount, but with 35% more deaths in Wuhan
and 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 was
delayed. Furthermore, the social distancing of working-age adults was most critical to
reducing COVID-19 outcomes versus social distancing among children and/or the
elderly.

Conclusions. Optimizing the timing of epidemic mitigation strategies is paramount and
involves weighing trade-offs between preventing infections and deaths and incurring
immense economic impacts. City-wide quarantine was not as effective as city-wide
social distancing due to its much higher daily cost than social distancing. Under typical
economic evaluation standards, the optimal timing for the full set of control measures
would have been much later than Jan 23, 2020 (status quo).

Note: Funding: We did not receive any funding support.

Competing Interest Declaration: The authors declare no competing interests.

Keywords: COVID-19, SARS-CoV-2, quarantine, social distancing, travel history screening, optimal strategy

JEL Classification: I10, I15