When enough members of a community are vaccinated, a sort of “immunity buffer” is created, adding an extra layer of protection for vaccinated individuals, while shielding those who are not eligible for particular vaccines, such as infants or people with compromised immune systems – individuals for whom disease-mortality rates are highest. This phenomenon is called “herd immunity,” and it has been vital to vaccines’ effectiveness.
当足够多数量的社区参与接种时，就会形成一种“社区缓冲”，给接种个体带来额外的保护，也为无法接种某些特殊疫苗的个体——比如婴儿或免疫系统功能不健全的人——提供了保护，他们都是疾病致死率最高的人群。这一现象被称为“群体免疫”，并且对疫苗的效果具有关键作用。