Claim of herd immunity reignites debate over UK's Covid-19 policy

LONDON • In the four months since Prime Minister Boris Johnson took a gamble by lifting virtually all of England's coronavirus restrictions, his country has settled into a disquieting new normal: more than 40,000 new cases a day and 1,000 or so deaths every week.

Yet those grim numbers have put Britain "almost at herd immunity", one of the government's most influential scientific advisers said this week. Herd immunity has been a much-discussed but elusive epidemiological state that some experts say could leave the country well placed to resist the fresh wave of infections now sweeping across continental Europe.

The comments, made by Professor Neil Ferguson, an epidemiologist at Imperial College in London - whose projections about the pandemic have often swayed government policy - are likely to revive the debate about Britain's status as a Covid-19 outlier: a country willing to tolerate a widely circulating virus and a steady death toll as the price of a return to economic normalcy.

They may also touch a nerve in a nation where herd immunity has been a fraught concept since it was raised by its chief scientific adviser Patrick Vallance in March last year as the virus was first bearing down. His openness to the advantages of herd immunity provoked such a backlash that the government has since rejected any suggestion that it embraces such a strategy.

Speaking on Tuesday, Prof Ferguson said he expected Britain to mostly avoid the spike in cases seen in Europe in recent weeks. This was in part, he said, because so many Britons had been infected since the lockdown was lifted in July, giving the population as a whole greater immunity. "We may well see a few weeks of slow growth, but we are in some sense almost at herd immunity," he said.

Other public health experts are sceptical of Prof Ferguson's theory, not least because Britain's high infection rate suggests there is still a large number of people with little or no immunity. They say it also does not take into account other factors, such as new variants or waning protection from vaccines.

"That's a bold statement," said Professor Devi Sridhar, head of the global public health programme at the University of Edinburgh. "I don't think modellers have enough data to assess whether we've reached the mythical herd immunity stage."

NYTIMES