New York City remains under seemingly interminable pandemic lockdown. But as researchers around the globe chase the promise of antibody tests—which have faced criticism for their mixed accuracy and dubious reputation as harbingers of COVID-19-immunity—a new wave of such testing in America’s largest city offered a glimmer of hope.

Mayor Bill de Blasio on Thursday detailed a plan to ramp up antibody testing locally, and specifically to survey about 140,000 people over two weeks in order to “understand COVID-19 spread and provide New Yorkers with more clarity,” as his office explained. Five testing sites will be set up in each of the five boroughs, according to the mayor, the idea being to provide free tests to 1,000 people per day by appointment through a hotline. Results from the tests will be available within 24 to 48 hours, he said…

“It will give us a lot more data about the extent of spread in New York, and they may even be able to say who was most at risk, who may have already had it, how it may have spread,” said Dr. Ania Wajnberg, an associate professor in the Department of Medicine & Department of Geriatrics and Palliative Medicine at the Icahn School of Medicine at Mount Sinai.