Assessment of COVID-19 Omicron epidemic trend in Shanghai based on time-varying reproduction number / 上海预防医学

ABSTRACT

ObjectiveTo assess the epidemic trend of COVID-19 Omicron and the effectiveness of containment measures in Shanghai by estimating the time-varying reproduction number （Rt）. MethodsBased on the daily reported confirmed cases and asymptomatic infections in Shanghai from February 20 to April 26， 2022， the R package "Epiestim"， which was built by Bayesian framework method， was used to estimate the variation curve of Rt during the epidemic period and to analyze the trend of the epidemic. ResultsIn the early stage of the epidemic， after the implementation of school closure and nuclear acid screening in some communities， Rt continued to fluctuate between 2.000 and 3.000， reaching a peak of 2.740 （95%CI： 2.640‒2.830） on March 21， but began to decline around one week after the city lock-down on April 1. As of April 18， the Rt value in Shanghai was below the threshold of 1.000 for the first time， reaching 0.955 （95%CI： 0.951‒0.961）. ConclusionAfter the implementation of public health measures with increasing strength of containment in Shanghai， the transmission rate gradually decreased， reflecting the effectiveness of the interventions. In the actual prevention and control process， the containment work should not be relaxed in order to keep the Rt below 1.000.