On Monday, 51 days after the first coronavirus case in New York, the state has begun conducting random antibody testing, administered on consenting grocery stores patrons in different regions across the state.

The procedure, also known as serology testing, uses a fingerstick blood sample and will analyze 3,000 people across New York, which has a population of 19.5 million, over the next week, Gov. Andrew Cuomo said Sunday in his daily news conference.

It comes as the number of total hospitalizations and intubations are down, along with the number of deaths. On Sunday, 478 people died from COVID-19 in New York state, bringing the state’s official total to 14,347.

“We are going to sample people in this state, thousands of people in this state, across the state to find out if they have the antibodies,” the governor said. “That will tell us, for the first time, what percent of the population actually has had the coronavirus and is now at least short-term immune to the virus. This will be the first, true snapshot of what we are really dealing with.”

While antibody testing has been around in the state, this is the first time that a random and mass testing is being initiated.

The test looks for the presence of antibodies, which are specific proteins made in response to infections, according to the Centers for Disease Control and Prevention (CDC). Their presence in the blood indicates that a person has had the disease.

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Scientists, though, are divided on whether the presence of antibodies means someone is now immune to the disease and the effectiveness of some tests is also under scrutiny.

Antibody testing has been lauded by officials as a crucial step in the process of restarting the economy, and identifying which people can safely return to work.

“The keys to reopening the economy are continuing to limit the spread of the virus and ramping up antibody testing,” Cuomo said last week.

New York’s PAUSE executive order, which closed nonessential business and schools, first came into effect on March 22, and will extend until May 15, at least. The economic impact of the virus in New York City alone, is expected to be $10 billion in lost revenue and a half million lost jobs.

“The problem is that these are tests that need to be validated and calibrated, and many of the tests out there don’t do that,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said Monday morning on TV, on “Good Morning America (GMA).” “So even though you hear about companies flooding the market with these antibody tests, a lot of them are not validated.”

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The FDA has approved four antibody tests under its emergency-use authorization, including Mount Sinai Laboratory, with more expected in the coming weeks. The authorization “will provide laboratories and providers with assurance that FDA has reviewed that test,” the agency said.

Wadsworth Center, a state-run lab in Albany, will be providing the antibody testing in New York, the state’s health department said. An inquiry as to whether Wadsworth Center has received or applied for the FDA’s emergency-use authorization was not immediately returned.

A further point of contention is regarding exactly how much immunity an antibody test proves.

“There’s an assumption—a reasonable assumption—that when you have an antibody that you are protected against reinfection, but that has not been proven for this particular virus,” Fauci said in the same GMA interview. “It’s true for other viruses, but we don’t know how long that protection, if it exists, lasts.”