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Antibody Testing Is Increasing, But A Positive Result Doesn't Prove Immunity

SCOTT SIMON, HOST:

More people are seeking out antibody tests to see if they've developed immunity to the coronavirus. But while those tests can offer some peace of mind, they might also give a false sense of security. NPR health correspondent Rob Stein joins us. Rob, thanks for being with us.

ROB STEIN, BYLINE: Morning, Scott.

SIMON: Let's begin with a reminder of what antibody testing is and moreover what it isn't.

STEIN: Yeah, so antibody tests are blood tests that look for proteins in the blood called antibodies that the immune system produces to fight off the virus. But it takes some time for the immune system to do that, so antibody tests are not used to try to spot people who just got infected or to figure out if a sick person has COVID-19. That's done with another kind of test that looks for genetic material from the virus in saliva or nose and throat swabs. Antibody tests are used to see if someone was exposed to the virus in the past and might have developed some immunity to the virus.

SIMON: What does some immunity mean if somebody tests positive for the antibodies?

STEIN: So, you know, Scott, that's the big question. The short answer is no one knows. It could turn out that the antibodies are protective or maybe just provide some protection, you know? Like, people with antibodies could still get sick but just not as sick. Or it could turn out that they only protect people for a little while or not at all. It's just unclear right now. And even though the FDA has started cracking down on antibody tests, there's still a lot of questions about the reliability of some of them.

SIMON: If that's the case, what's the point of getting an antibody test?

STEIN: Researchers want to do a lot of antibody testing to try to get a better handle on the epidemic. There's been a big shortage of tests that diagnose new infections. And that's left the country kind of flying blind in really knowing where the virus is spreading and how much it spread. So an antibody test could be really valuable for getting a much better big picture of the epidemic. That said, antibody testing is now increasingly also being used to provide information to individual people to see if they might have developed some immunity against the virus, even if it's unclear what that means.

SIMON: Do we know who's trying to get these tests and how they're being used right now?

STEIN: Yes. So some employers are requiring employees to get antibody testing to either keep working or to come back to work. Some are using it to figure out how widespread the virus is, you know, on their - like, on their factory floors or in other workplaces and to try to get, you know, a better sense of how they could improve worker safety. And some labor unions are offering the testing to their members to give them some sense of security. And some people are just seeking out antibody tests themselves because they're curious if that, you know, nasty illness they had a couple months ago was COVID and whether they might possibly have some immunity now, just to maybe let down their guard just a little bit.

SIMON: But given all the uncertainty that you just sketched out about the test, would that even be a good idea?

STEIN: Yes, so that's the issue. It makes many doctors and public health experts very nervous, you know, that people with antibodies will do risky things, you know, like stop wearing their masks or start having big parties or go visit their elderly parents or grandparents and that employers may not take adequate steps to protect employees they think have immunity. You know, I've been talking to lots of people about antibody testing, and it's clear that there's a lot of misconceptions about what having antibodies means - like, having antibodies means you can't catch the virus again or you can't spread it to someone else. That's still possible. All that said, some experts say there is a chance that the antibodies could offer some protection. So if someone in the family, for example, has to go to the pharmacy or grocery store or go back to work, maybe the one with antibodies could be the safest bet for that. It's just really important that they know it's no guarantee, and they still have to be very careful.

SIMON: NPR health correspondent Rob Stein, thanks so much for being with us.

STEIN: You're welcome, Scott. Transcript provided by NPR, Copyright NPR.