摘要目的:评估新型冠状病毒Omicron变异株在北京市现有防控措施下的传播力，为做好疫情防控工作提供参考依据。方法:收集北京市2022年3月7-25日报告的78例具有明确传播链的Omicron变异株感染者信息，分别采用Gamma和Weibull分布拟合潜伏期和序列间隔时间，使用马尔科夫链蒙特卡罗算法估计实时再生数（ R t）。 结果:Omicron变异株感染者潜伏期 M（ Q1， Q3）为4.0（3.0，6.0）d，序列间隔时间3.0（2.0，5.0）d，序列间隔时间在未完成和已完成全程疫苗接种感染者中 M（ Q1， Q3）分别为2.0（1.0，4.0）d和4.0（2.0，6.0）d（ Z=-2.12， P=0.034），儿童和成年人感染者分别为2.0（1.5，3.0）d和4.0（2.0，6.0）d（ Z=-2.02， P=0.044），差异均有统计学意义。本轮疫情 R t初始值为4.98（95% CI：2.22~9.04）。 结论:与既往Delta变异株相比，北京市Omicron变异株的传播力较强，应持续做好常态化疫情防控和新型冠状病毒疫苗接种工作，关注儿童易感人群。

abstractsObjective:To evaluate the transmissibility of 2019-nCoV Omicron variant under the current prevention and control strategy in Beijing, and provide evidence for the prevention and control of COVID-19.Methods:The information of 78 Omicron variant infection cases involved in clear transmission chains in Beijing during 7-25 March, 2022 were collected, the incubation period and serial interval of the disease were fitted by using Gamma and Weibull distribution. Markov Chain Monte Carlo approach was used to estimate the time-varying reproduction number ( R t). Results:The median of the incubation period ( Q1, Q3) of Omicron variant infection was 4.0 (3.0, 6.0) days, and the serial interval was 3.0 (2.0, 5.0) days. The median of the serial interval ( Q1, Q3) was 2.0 (1.0, 4.0) days in unvaccinated cases and 4.0 (2.0, 6.0) days in vaccinated cases ( Z=-2.12, P=0.034), and 2.0 (1.5, 3.0) days in children and 4.0 (2.0, 6.0) days in adults, respectively ( Z=-2.02, P=0.044), the differences were significant. The mean of R t was estimated to be 4.98 (95% CI: 2.22-9.04) for Omicron variant in this epidemic. Conclusion:Omicron variant has stronger transmissibility compared with Delta variant. It is necessary to strengthen the routine prevention and control COVID-19, promote the vaccination and pay close attention to susceptible population, such as children.