How to Understand Herd Immunity in the Context of COVID-19

COVID-19 is an emerging rapidly evolving situation, which is widely disseminated all over the world. During this period, the concept of herd immunity is often mentioned, but it is easily misunderstood. In the context of COVID-19, this article comprehensively expounds the concept and purpose of herd immunity, the necessary conditions for realizing the herd immunity, the restrictive conditions for the application of herd immunity, and the challenges faced by the realization of herd immunity. Furthermore, starting from the "three elements," which refers to the characteristics of the pathogen and the population, as well as the behaviors taken by the population, the relationship between herd immunity and COVID-19 is deeply analyzed. Based on the aforementioned, the implementation of corresponding measures is expected to slow down the spread of the epidemic and even eliminate pathogens.