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

We tracked the effective reproduction number Rt of 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 10-14 and self-reported to have been previously test-positive. After the announcement of "20 measures", we estimated that Rt increased to 3.42 (95% CrI: 2.79-4.17) on November 18. Infection incidence peaked on December 10, and the cumulative infection attack rate was 42.5% (95% CrI: 20.3-63.9) on December 14. Surveillance programmes should be rapidly set up to monitor the evolving epidemiology and evolution of SARS-CoV-2 across China.