Rejoinder of "The timing and effectiveness of implementing mild interventions of COVID-19 in large industrial regions via a synthetic control method"

The outbreak of novel coronavirus disease (COVID-19) has spread around the world since it was detected in December 2019 The Chinese government executed a series of interventions to curb the pandemic The "battle" against COVID-19 in Shenzhen, China is valuable because populated industrial cities are the epic centres of COVID-19 in many regions We made use of synthetic control methods to create a reference population matching specific characteristics of Shenzhen With both the synthetic and observed data, we introduced an epidemic compartmental model to compare the spread of COVID-19 between Shenzhen and its counterpart regions in the United States that didn't implement interventions for policy evaluation Once the effects of policy interventions adopted in Shenzhen were estimated, the delay effects of those interventions were referred to provide the further control degree of interventions Thus, the hypothetical epidemic situations in Shenzhen were inferred by using time-varying reproduction numbers in the proposed SIHR (Susceptible, Infectious, Hospitalized, Removed) model and considering if the interventions were delayed by 0 day to 5 days The expected cumulative confirmed cases would be 1546, which is 5 75 times of the observed cumulative confirmed cases of 269 in Shenzhen on February 3, 2020, based on the data from the counterpart counties (mainly from Broward, New York, Santa Clara, Pinellas, and Westchester) in the United States If the interventions were delayed by 5 days from the day when the interventions started, the expected cumulative confirmed cases of COVID-19 in Shenzhen on February 3, 2020 would be 676 with 95% credible interval (303,1959) Early implementation of mild interventions can subdue the epidemic of COVID-19 The later the interventions were implemented, the more severe the epidemic was in the hard-hit areas Mild interventions are less damaging to the society but can be effective when implemented early