Estimating the transmission dynamics of SARS-CoV-2 Omicron BF.7 in Beijing after the adjustment of zero-COVID policy in November - December 2022.

We tracked the effective reproduction number R t of the predominant SARS-CoV-2 variant Omicron BF.7 in Beijing in November - December 2022 by fitting a transmission dynamic model parameterized with real-time mobility data to (i) the daily number of new symptomatic cases on November 1-11 (when China's zero-COVID interventions were still strictly enforced) and (ii) the proportion of individuals who participated in online polls on December 10-22 and self-reported to have been test-positive since November 1. After China's announcement of '20 measures' to transition from zero-COVID, we estimated that R t increased to 3.44 (95% CrI: 2.82-4.14) on November 18 and the infection incidence peaked on December 11. We estimated that the cumulative infection attack rate (that is the proportion of population who have been infected since November 1) in Beijing was 75.7% (95% CrI: 60.7-84.4) on December 22, 2022, and 92.3% (95% CrI: 91.4-93.1) on January 31, 2023. Surveillance programmes should be rapidly set up to monitor the evolving epidemiology and evolution of SARS-CoV-2 across China.