“I believe the substantial epidemics in Arizona, Florida and Texas will leave enough immunity to assist in keeping COVID-19 controlled,” Trevor Bedford, a pandemic analyst at the University of Washington, said on Friday, in a series of tweets. “However, this level of immunity is not compatible with a full return to societal behavior as existed before the pandemic.”…

What is certain is that in the US, with a raging epidemic, natural immunity is building fast. During June and July, Gu estimates, 450,000 people a day were being infected by the coronavirus in the US, the highest figures since the disease arrived in February.

That number is higher than the official case count because it includes an estimate of infections that go unseen, unfelt, or unreported. In June, CDC director Robert Redfield told reporters that the real number of infections could be many times the official tally. For instance, Gu has estimated that about 35 million Americans have now been infected—roughly 10% of the nation’s population.

Natural infection also turns out to be extremely efficient at reducing virus transmission—even more effective than an equal number of people getting a vaccine.