摘要
The coronavirus disease 2019(COVID-19)pandemic has caused infection in more than 400 million people,and 5.8 million deaths.The most recent outbreak was caused by the Omicron variant,which was first identified in South Africa on November 11,2021.It has spread to more than 150 countries thus far.The fast spread of theOmicron variant has caused great concernworldwide.Compared to the previous outbreaks of COVID-19 variants,the Omicron outbreak is much larger.As shown in Figure 1A,a sharp surge appeared in approximately January 2022.