What if herd immunity is closer than scientists thought?

Now some researchers are wrestling with a hopeful possibility. In interviews with The New York Times, more than a dozen scientists said that the threshold is likely to be much lower: just 50 percent, perhaps even less. If that’s true, then it may be possible to turn back the coronavirus more quickly than once thought.

The new estimates result from complicated statistical modeling of the pandemic, and the models have all taken divergent approaches, yielding inconsistent estimates. It is not certain that any community in the world has enough residents now immune to the virus to resist a second wave.

But in parts of New York, London and Mumbai, for example, it is not inconceivable that there is already substantial immunity to the coronavirus, scientists said.

“I’m quite prepared to believe that there are pockets in New York City and London which have substantial immunity,” said Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health. “What happens this winter will reflect that.”