Liu Hengcong, Zhang Juanjuan, Cai Jun, Deng Xiaowei, Peng Cheng, Chen Xinghui, Yang Juan, Wu Qianhui, Chen Xinhua, Chen Zhiyuan, Zheng Wen, Viboud Cécile, Zhang Wenhong, Ajelli Marco, Yu Hongjie
Department of Infectious Diseases, Huashan Hospital, School of Public Health, Fudan University, Shanghai, China.
Key Laboratory of Public Health Safety, Fudan University, Ministry of Education, Shanghai, China.
medRxiv. 2021 Sep 14:2021.07.23.21261013. doi: 10.1101/2021.07.23.21261013.
To allow a return to a pre-COVID-19 lifestyle, virtually every country has initiated a vaccination program to mitigate severe disease burden and control transmission. However, it remains to be seen whether herd immunity will be within reach of these programs.
We developed a data-driven model of SARS-CoV-2 transmission for China, a population with low prior immunity from natural infection. The model is calibrated considering COVID-19 natural history and the estimated transmissibility of the Delta variant. Three vaccination programs are tested, including the one currently enacted in China and model-based estimates of the herd immunity level are provided.
We found that it is unlike to reach herd immunity for the Delta variant given the relatively low efficacy of the vaccines used in China throughout 2021, the exclusion of underage individuals from the targeted population, and the lack of prior natural immunity. We estimate that, assuming a vaccine efficacy of 90% against the infection, vaccine-induced herd immunity would require a coverage of 93% or higher of the Chinese population. However, even when vaccine-induced herd immunity is not reached, we estimated that vaccination programs can reduce SARS-CoV-2 infections by 53-58% in case of an epidemic starts to unfold in the fall of 2021.
Efforts should be taken to increase population's confidence and willingness to be vaccinated and to guarantee highly efficacious vaccines for a wider age range.
为了让人们回归到新冠疫情前的生活方式，几乎每个国家都启动了疫苗接种计划，以减轻严重疾病负担并控制传播。然而，这些计划能否实现群体免疫仍有待观察。
我们为中国建立了一个由数据驱动的新冠病毒传播模型，中国人群因自然感染而产生的既往免疫力较低。该模型在考虑新冠病毒自然史和德尔塔变异株估计传播力的情况下进行了校准。测试了三种疫苗接种计划，包括中国目前实施的计划，并提供了基于模型的群体免疫水平估计。
我们发现，鉴于2021年全年中国使用的疫苗效力相对较低、目标人群中未将未成年人纳入以及缺乏既往自然免疫力，德尔塔变异株不太可能实现群体免疫。我们估计，假设疫苗对感染的效力为90%，疫苗诱导的群体免疫将需要覆盖93%或更高比例的中国人口。然而，即使未达到疫苗诱导的群体免疫，我们估计在2021年秋季疫情开始爆发的情况下，疫苗接种计划可将新冠病毒感染减少53%-58%。
应努力提高民众接种疫苗的信心和意愿，并确保为更广泛年龄范围的人群提供高效疫苗。
