Mar. 21. 2020

Prime Minister Boris Johnson of Britain once said his political hero was the mayor in the film “Jaws,” praising him for defying mass hysteria to keep the beaches open after a constituent is eaten by a shark.

While countries across Europe have shut schools, sporting events and even restaurants and bars, Johnson has largely kept Britain open, opting for more targeted measures like asking people with respiratory symptoms to stay home. In effect, his government has said that mass closures will not halt the outbreak, and that exposing a large segment of the population will help build immunity and limit future infections.

That strategy has startled some epidemiologists, drawn criticism from a former health secretary and political ally, and prompted angry demands that Johnson’s government reveal more of its reasoning.

Herd immunity, a term usually used to refer to the way mass vaccinations can stop the spread of disease and protect people who are not immune, is not seen by many scientists as a tool to be used against the coronavirus.

“Herd immunity means 70% of people or so have been infected,” said Martin Hibberd, a professor of infectious diseases at the London School of Hygiene and Tropical Medicine.” In my mind, that’s not a desirable aim. That’s a kind of consequence of the strategy.”

And he said the government’s approach may not rely enough on testing. Without knowing whether Britain is suffering a more concentrated outbreak, as in the north of Italy, or whether its death rate is as low as it believes, it is difficult to craft the right response.

“If there’s something I feel is missing,” he said, “it’s that they haven’t tested sufficiently.”