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More People Are Relying On COVID-19 Tests, But Experts Say They're Not Foolproof


The delta virus is surging just as children are going back to school and more businesses are trying to reopen. That also causes a surge in testing, too. To tell us more about the state of testing in the United States, we're joined by NPR health correspondent Rob Stein. Rob, thanks so much for being with us.

ROB STEIN, BYLINE: My pleasure, Scott.

SIMON: Remind us again, please. What kind of at-home COVID-19 tests can people get these days?

STEIN: Yeah, so, you know, there are a slew of these at-home, over-the-counter COVID tests now, and they're much easier and faster than those PCR tests. You know, there's no need for prescription or a doctor's visit or waiting in line at a test site or waiting for the results to finally come in. The most well-known of these are those antigen tests, and they look for pieces of the virus instead of the genetic material that the PCR test uses. You can order them online or you can pick them up at your local drugstore. You swab yourself at home and get results in 15 minutes, instead of waiting hours or days. So they're really super fast and easy.

SIMON: A lot of parents seem to be stocking up on these at-home tests so they can decide whether or not it's safe to send their children to school. Is stockpiling a good idea?

STEIN: You know, these tests are especially good at spotting someone who's infected when they have symptoms and when they're the most infectious, meaning they have a lot of virus in their noses and are most likely to spread it to somebody else. But like any test, you know, they're not perfect, especially, you know, right after someone just got exposed and before there's much virus growing in them yet. They can miss people who are infected. And people have to use them correctly. You know, they can mess it up if they don't swab properly or they don't follow the instructions carefully.

But they are being used by lots of people for lots of reasons, including parents that test their kids. And I've gotten, you know, kind of a mixed reaction when I've talked to experts about that. Many said they'd feel quite comfortable relying on the results, especially if their kid has symptoms. For example, here's Gigi Gronvall. She studies testing at Johns Hopkins and has two young kids yourself.

GIGI GRONVALL: That's how I use them myself. I mean, they're really good for that immediate peace of mind. My 11-year-old has sometimes some allergies, and he was sniffly. And so I wanted to just make sure that it was indeed allergies. And so this test is really good for that.

STEIN: You know, others are a little less enthusiastic. Susan Butler-Wu at the University of Southern California - she gives her kids an antigen test every Monday morning to help keep COVID out of their school. But she knows the results only tell you so much.

SUSAN BUTLER-WU: I think the way to think about it is, you're less likely to be infectious at this moment in time. That answer could be different when you retest in a couple hours. No test is perfect. So I don't view these as a free pass to decide, based on this one swab that went up both of my nostrils for a couple of seconds on each side, that I have a definitive declaration of non-infectiousness.

STEIN: So she gets her kids a PCR test if she wants to know for sure whether they're infected, especially if they test negative on an antigen test, even though they have symptoms. And you know, these tests are not cheap. They're, like, $25 for two tests.

SIMON: And are there enough tests? We've heard about testing shortages early in the pandemic.

STEIN: You know, things are way better than they were. Most of the supply shortages have been solved, at least for now. And you know, PCR labs say they're getting results back within a day or so for the most part. That said, you know, a lot of testing sites became vaccination sites. And now that the demand for testing is surging again, lines are forming again in some places, and it's starting to sometimes take days to get those results.

And there's been such a run on those fast tests that they can be really hard to get now. You know, CVS is now limiting online sales to six boxes and in-store sales to four. And you know, I should note that the percentage of people testing positive right now is still pretty high again, which means we're not doing nearly enough testing to catch people before they might spread the virus.

SIMON: NPR health correspondent Rob Stein, thanks so much.

STEIN: You bet, Scott.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

Rob Stein is a correspondent and senior editor on NPR's science desk.