Herd immunity is a key concept for epidemic control. It states that only a proportion of a population needs to be immune (through overcoming natural infection or through vaccination) to an infectious agent for it to stop generating large outbreaks. A key question in the current COVID-19 pandemic is how and when herd immunity can be achieved and at what cost. During the current COVID-19 pandemic, the concept of herd immunity has become a topic of much debate. This Comment examines the factors that determine it, discusses how far we have come and considers what it will take to reach herd immunity safely.

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COVID-19 群体免疫：我们在哪里？

群体免疫是流行病控制的一个关键概念。它指出，只有一部分人口需要对传染源免疫（通过克服自然感染或通过疫苗接种），才能停止产生大规模爆发。当前 COVID-19 大流行的一个关键问题是如何以及何时可以实现群体免疫，以及需要付出什么代价。在当前的 COVID-19 大流行期间，群体免疫的概念已成为备受争议的话题。本评论检查了决定它的因素，讨论了我们已经走了多远，并考虑了如何安全地实现群体免疫。