Estimating the transmission dynamics of Omicron in Beijing, November to December 2022

We tracked the effective reproduction number R t of SARS-CoV-2 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 the 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 previously test-positive since November 1. After the announcement of “20 measures”, 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. The cumulative infection attack rate (i.e. the proportion of population who have been infected since November 1) was 43.1% (95% CrI: 25.6 – 60.9) on December 14 and 75.7% (95% CrI: 60.7 – 84.4) on December 22. Surveillance programmes should be rapidly set up to monitor the evolving epidemiology and evolution of SARS-CoV-2 across China.