群体免疫
Herd immunity


1月14日，在印度尼西亚雅加达的西普托•曼贡库苏莫医院，印尼卫生部副部长萨克索诺（中）接种中国科兴公司的克尔来福新冠疫苗。新华社记者 叶平凡摄 图源：新华网

世界卫生组织的首席科学家苏米娅•斯瓦米纳坦1月11日表示：“我们不可能在2021年实现任何程度的人群免疫或群体免疫。”同时她还强调，继续推行保持距离、勤洗手、佩戴口罩等措施对于在接下来的这一年控制新冠疫情传播很有必要。当足够多的人口对一种传染病免疫，从而防止了疫病传播，群体免疫就实现了。卫生专家指出，阻止群体免疫实现的因素包括发展中国家获得疫苗的能力有限、民众对接种疫苗的质疑以及病毒变异的可能性。

"We are not going to achieve any levels of population immunity or herd immunity in 2021," World Health Organization (WHO) chief scientist Soumya Swaminathan told a briefing, while emphasizing that measures like physical distancing, hand washing and mask wearing continue to be necessary in containing COVID's spread for the rest of the year. Herd immunity occurs when enough people in a population have immunity to an infection so that it prevents the disease from spreading. Mitigating factors to herd immunity include limited access to vaccines in developing countries, skepticism over vaccination, and the potential for virus mutations, according to health experts.