Will Antibody Tests Help Us Leave Quarantine?

Debbie Koenig

April 13, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

With more than 90% of the country unable to leave home for work or school, officials have said one thing might help us get back to normal: a rapid blood test to see if someone has developed immunity to COVID-19.

Serologic tests, as they're called, look for antibodies in the blood. Antibodies develop when you've been exposed to a particular infection, and experts believe many COVID-19 cases are so mild people may not know they had it. That means there's a chance a significant number of us have developed antibodies already.

Hoping to discover just how widespread the virus has become, last week the National Institutes of Health (NIH) announced they're looking for 10,000 volunteers with no confirmed history or current symptoms of COVID-19. Researchers want to see how many have antibodies in their blood.

"We don't currently have good numbers for the numbers of people who are infected now, much less people who were infected before who were never tested," Angela Rasmussen, MD, a virologist at Columbia University in New York, told The New York Times. "So it's really important from an epidemiological perspective to do these types of serology assays."

The NIH is far from the only organization working on this. In March, the FDA announced a policy that would allow commercial labs meeting certain conditions to market their tests without waiting for the FDA approval known as an Emergency Use Authorization (EUA). More than 70 of those tests are on the horizon. Only one test has received an EUA.

"Within a period of a week or so, we're going to have a rather large number of tests that are available," Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, recently told CNN.

But experts warn that the presence of antibodies alone doesn't necessarily indicate you're cleared to reenter the world. First of all, there are several types of antibodies. Only a subset known as neutralizing antibodies can block the virus.

"We don't know which antibody response neutralizes the virus," says Joseph Vinetz, MD, a professor of infectious diseases at Yale University. "Once you have an antibody test, you have to study people with antibody responses for their risk for getting a new infection."

That won't happen, he says, until enough people who test positive for antibodies return to the workforce — and then either get reinfected or don't. It's a waiting game.

"If the governor of a state says, 'We have an antibody test, I can release people back to work,' the data don't really support that at this point," Vinetz says. "We'll find out what happens when policy gets balanced against science."

Then there's the magnitude of the challenge of testing everybody. With more than 300 million people in the US, the 3 million diagnostic tests performed to date represent barely 1% percent of the population. On Saturday, Admiral Brett Giroir, the testing "czar" on Trump's coronavirus task force, told Bloomberg News that by May the country should be "in the ballpark" of capacity for widespread diagnostic and antibody testing.

Unreliable tests may pose another problem. In the UK, Spain, and elsewhere, false test results have dashed hopes for a quick, accurate test. And in the US, the FDA's decision to relax oversight for antibody tests may backfire.

"It really has created a mess that's going to take a while to clean up," Eric Blank, DrPH, senior director at the Association for Public Health Laboratories, told ABC News. "In the meantime, you've got a lot of companies marketing a lot of stuff and nobody has any idea of how good it is."

For now, at least, no test can tell you if you're safe to go back to your regular daily life. No testing company has made enough tests to garner large-scale results. And though you may see tests claiming otherwise, none has been specifically approved by the FDA.

"If you see [tests] on the internet, do not buy them until we can give you a test that's reliable for all Americans," Deborah Birx, MD, coordinator of the White House coronavirus task force, said at a recent briefing.

Given all the uncertainty surrounding antibody tests, "what we really need is a pill that reduces the amount of time that somebody is ill or infectious for other people, or that might prevent people from getting infected to begin with," Vinetz says. The Yale School of Medicine, where he works, and Yale New Haven Health System are working on that. They're establishing a drive-through COVID-19 clinical research platform for patients with mild or asymptomatic cases, which Vinetz hopes will open in the next few weeks. Those who test positive will be given either an experimental antiviral drug or a placebo, then asked to return for daily swabs for 1 week to check the amount of the virus in their throats, with weekly monitoring after that.

Vinetz anticipates having preliminary results within 2 weeks of the platform launching.

"Right now, people can have this virus for a couple of weeks," Vinetz says. "What if you were only infectious for 2 days? If a drug really kills the virus, not only can you treat people who have the infection, if the drug is safe, you can give it to people as prophylaxis."

This story first appeared on WebMD.