The precise herd immunity threshold for the novel coronavirus is not yet clear, but several experts said they believed it would be higher than 60 percent. Carl Bergstrom comments on herd immunity in a New York Times article. 

Studies that use these tests to examine a cross section of a population, often called serology surveys, are being undertaken around the country and the world.

These studies are far from perfect, said Carl Bergstrom, a professor of biology at the University of Washington. But in aggregate, he said, they give a better sense of how far the coronavirus has truly spread — and its potential for spreading further.

The herd immunity threshold may differ from place to place, depending on factors like density and social interaction, he said. But, on average, experts say it will require at least 60 percent immunity in the population. If the disease spreads more easily than is currently believed, the number could be higher. If there is a lot of variation in people’s likelihood of becoming infected when they are exposed, that could push the number down.

All estimates of herd immunity assume that a past infection will protect people from becoming sick a second time. There is suggestive evidence that people do achieve immunity to the coronavirus, but it is not yet certain whether that is true in all cases; how robust the immunity may be; or how long it will last.