A pair of controversial surveys in the Bay Area and Los Angeles County found antibodies in 2.5 to 4 percent of the population—and even those numbers may be overestimates due to methodological flaws. In New York City, the country’s COVID-19 epicenter, 24.7 percent of people tested positive for antibodies. (The statewide number is 14.9 percent.) These rates do translate to many times more cases than officially documented, to be clear, but they are still a far cry from the 70 percent scientists believe is necessary to reach herd immunity and stop disease transmission. And if only a small fraction of the population can return to work without fear of getting the coronavirus, a return to something resembling normal is still a long way off.
“I think there was a lot of hope that we would do the antibody testing or do the serosurveys and then we would see there was a huge amount of immunity built up in the population,” Natalie Dean, a biostatistician at the University of Florida, told me. But earlier data from outside the U.S. have suggested otherwise. One study in the hard-hit municipality of Gangelt, considered “Germany’s Wuhan,” found 14 percent of people testing positive for antibodies. “It was clear from that point, for me, that we weren’t going to see big numbers,” Dean said.