Different transmission dynamics of COVID-19 and influenza suggest the relative efficiency of isolation/quarantine and social distancing against COVID-19 in China

BACKGROUND: Non-pharmaceutical interventions (NPIs) against Coronavirus Disease 2019 (COVID-19) are vital to reducing the transmission risks However, the relative efficiency of social distancing against COVID-19 remains controversial, since social distancing and isolation/quarantine were implemented almost at the same time in China METHODS: In this study, surveillance data of COVID-19 and seasonal influenza in the year 2018-2020 were used to quantify the relative efficiency of NPIs against COVID-19 in China, since isolation/quarantine was not used for the influenza epidemics Given that the relative age-dependent susceptibility to influenza and COVID-19 may vary, an age-structured Susceptible-Infected-Recovered model was built to explore the efficiency of social distancing against COVID-19 under different population susceptibility scenarios RESULTS: The mean effective reproductive number, Rt, of COVID-19 before NPIs was 2 12 (95% confidential interval (CI): 2 02-2 21) By March 11, 2020, the overall reduction in Rt of COVID-19 was 66 1% (95% CI: 60 1%-71 2%) In the epidemiological year 2019/20, influenza transmissibility reduced by 34 6% (95% CI: 31 3%-38 2%) compared with that in the epidemiological year 2018/19 Under the observed contact patterns changes in China, social distancing had similar efficiency against COVID-19 in three different scenarios By assuming same efficiency of social distancing against seasonal influenza and COVID-19 transmission, isolation/quarantine and social distancing could lead to a 48 1% (95% CI: 35 4%-58 1%) and 34 6% (95% CI: 31 3%-38 2%) reduction of the transmissibility of COVID-19 CONCLUSIONS: Though isolation/quarantine is more effective than social distancing, given that typical basic reproductive number of COVID-19 is 2-3, isolation/quarantine alone could not contain the COVID-19 pandemic effectively in China