【时事】“群体免疫”靠谱吗？英国这步险棋的真正考量是什么？

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“群体免疫”靠谱吗？英国这步险棋的真正考量是什么？
Herd immunity: will the UK's coronavirus strategy work?

Herd immunity is a phrase normally used when large numbers of children have been vaccinated against a disease like measles, reducing the chances that others will get it. As a tactic in fighting a pandemic for which there is no vaccine, it is novel – and some say alarming.

It relies on people getting the disease and becoming immune as a result. But allowing the population to build up immunity in this way could increase the risk to the most vulnerable: older people with underlying health problems.

To reach herd immunity, about 60% of the population would need to get ill and become immune, according to Sir Patrick Vallance, the government’s chief scientific adviser. Though it could need as much as 70% or more. Even scientists who understand the strategy are anxious.

The government seems to favour this strategy. Dr David Halpern, a psychologist who heads the Behavioural Insights Team, said on BBC News: “There’s going to be a point, assuming the epidemic flows and grows, as we think it probably will do, where you’ll want to cocoon, you’ll want to protect those at-risk groups so that they basically don’t catch the disease and by the time they come out of their cocooning, herd immunity’s been achieved in the rest of the population.”

Herd immunity might not even last, Anthony Costello, a pediatrician and former World Health Organization director, said. “Does coronavirus cause strong herd immunity or is it like flu where new strains emerge each year needing repeat vaccines? We have much to learn about Co-V immune responses.” Vaccines, he said, were a much safer way of bringing it about.