Why Antibody Testing Is Needed to Understand the Full Reach of the Coronavirus Outbreak

The number of confirmed cases of the new coronavirus in the U.S. may be climbing every day, but the true magnitude of the crisis remains still unclear, largely due to a severe lack of testing kits.

Until more testing becomes available, only people who have come in close contact with a confirmed case or have a fever are typically getting tested. That leaves out asymptomatic people or those with mild cases not requiring hospitalization — people who could be unknowingly spreading COVID-19 by going about their daily lives.

In an effort to identify more cases of COVID-19, researchers are now working on a test that would use blood to check for antibodies to the virus. The test would also help determine if people who had the virus become immune to it, which could inform how to handle the outbreak moving forward, as well as aid in the development of vaccines and treatments.

Virologists at the Icahn School of Medicine at Mount Sinai shared initial details of an antibody test on March 18, which, along with tests already available, could help identify thousands more cases each day and inform researchers about immunity, Science magazine reported.

The antibody test would identify any stage of the virus, whereas the existing nasal swab version can only identify if someone is currently infected with the virus, and cannot detect if they are carrying COVID-19 and are asymptomatic.

“What that’s measuring is: ‘Has your body ever seen the virus?’ ” Laurie Garrett, a Pulitzer Prize-winning science journalist explained to New York Magazine. “That’s useful in two ways. As a diagnostic, it gives the refined information: ‘Yes, you have this in you at the moment.’ It also can guide the activities of the physician, who might say, ‘Gee, I’ve got a pneumonia patient, I wonder if they’ve ever had COVID?’ ”

“But the most important thing is that that test can be a public health tool,” she continued. “If we had this antibody test, we can go around randomly selecting people in New York City and find out how many New Yorkers, including right now, have had this virus in their bodies. Since we know the virus has never been in human beings before, anybody who has antibodies against it has been exposed since January.”

Garrett said that antibody testing would be a “game changer,” because it would help policymakers see how long the virus has been around. If it’s only been in New York City since February, for example, then “we’re going to suddenly skyrocket and our hospitals are going to be overwhelmed.”

“But if, by contrast, the same number of cases are found in the historic samples going back to the first of January, that would tell us, ‘Okay, it’s gradually unfolding, we don’t have to go down to lockdown every single person in New York, we may be able to flatten the curve.’ ”

And down the line, antibody testing could eventually show how long any immunity lasts, and what types of vaccines are needed, Science reported.

As information about the coronavirus pandemic rapidly changes, PEOPLE is committed to providing the most recent data in our coverage. Some of the information in this story may have changed after publication. For the latest on COVID-19, readers are encouraged to use online resources from CDC, WHO, and local public health departments and visit our coronavirus hub.

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