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What we know about COVID-19 antibodies — and what we don’t

Scientists say antibody testing could be a key tool in the fight against the novel coronavirus. Still, many questions remain about the accuracy of antibody testing. The Food and Drug Administration has tried to crack down on inaccurate tests, but scientists aren’t even sure yet what a positive test means for immunity. John Yang reports.

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  • Judy Woodruff:

    Scientists say antibody testing may eventually be a key tool in the fight against COVID-19.

    There was encouraging news on that front this week. Researchers said that antibodies found in a patient who had the coronavirus connected to SARS 17 years ago were able to neutralize COVID-19.

    Still, many questions remain about the effectiveness of antibody testing and what a positive test means for immunity.

    John Yang has the story.

  • John Yang:

    Around the world, an increasing demand for antibody tests, as people try to find out if they have been exposed to the coronavirus.

    Patrick Easley was tested in Chicago.

  • Patrick Easley:

    My thinking was, if I got the antibody test, and if it came back positive, that means that I already had COVID, and it had already gotten through my system, and that I should be A-OK-ish.

  • John Yang:

    In West Texas, Coyne Gibson drove three hours to get tested.

  • Coyne Gibson:

    My rationale comes from my science and engineering background and that, you know, knowing is better than guessing.

  • John Yang:

    Sara Cureton said she was the sickest she's ever been in mid-January, and was surprised when her antibody test was negative.

  • Sara Cureton:

    The question has changed from, did I have it, can I help someone, to, how accurate is that test?

  • John Yang:

    That's the question even scientists are asking.

    Gigi Kwik Gronvall is a senior scholar at the Johns Hopkins Center For Health Security.

  • Gigi Kwik Gronvall:

    There are a lot of things we don't know about the antibodies. It's not the simple black/white, yes/no, go/no-go type of decision-making tool that I think people want it to be.

  • John Yang:

    Antibodies are a crucial part of our immune system. They attach to viruses, or virus-infected cells, and ideally, neutralize them, helping our body remove them.

    Testing for antibodies is different from testing for the virus itself. Antibody tests rely on a blood sample. A positive result indicates exposure to the virus and an immune response to it, even if you never have symptoms, or at least that's the goal.

    These tests, especially for a new virus like COVID-19, can be wrong.

  • Gigi Kwik Gronvall:

    Somebody may get the information that they have been exposed, and then they think, oh, I'm good to go, and then it turns out they were actually vulnerable, and they could get sick themselves and then transmit it to others.

  • John Yang:

    In March, under pressure to quickly ramp up testing, the Food and Drug Administration allowed manufacturers to start distributing tests without confirming their accuracy. The market was flooded with more than 150 of them.

  • Gigi Kwik Gronvall:

    It was kind of a let 1,000 flowers bloom strategy. And that led to a lot of tests being less accurate than advertised.

  • John Yang:

    Earlier this month, the agency began requiring that test makers prove their products are accurate, or risk having them pulled from the market.

    But even if every antibody test was completely reliable, that wouldn't tell us much about immunity. That's because scientists don't know yet if antibodies protect someone from getting COVID-19 again. So, who should get an antibody test right now, and why?

    What's the right reason somebody should want to get an antibody test?

  • Gigi Kwik Gronvall:

    I don't fault people for wanting to know if that terrible, terrible sickness they had a couple of months ago, if that really was COVID-19.

    But, you know, you just — I just hope that people understand the limitations of our knowledge.

  • John Yang:

    Even so, doctors across the country are making tests widely available.

  • Rahul Kharee:

    It's important. And we are opening it up to anyone who wants it. People are saying — are going to say, you're overtesting. They're going to go, you are overtesting.

    But we're not. We're screening.

  • Katharine Miao:

    We do, you know, rapid flus with that, knowing — we know that they're not perfect. Rapid strep tests, they're not perfect. But it helps better inform the patient and it helps people make decisions for their own lives.

  • John Yang:

    Stanford University bioethicist Hank Greely sees it differently.

  • Hank Greely:

    I think the tests are not good enough to be pushed for almost all of them. And people don't need them at this point. If there are good tests, they should be used for important scientific research.

  • John Yang:

    Studies from California to Massachusetts have tried to use antibody tests to draw conclusions about the prevalence of the virus.

    In New York City, researchers estimate that one in five residents was likely exposed. And researchers recently announced results from what they called the first nationwide antibody study. They tested about 5,600 Major League Baseball employees.

    The result? An estimated positive rate of less than 1 percent.

    One of the study's lead researchers, Daniel Eichner of the anti-doping Sports Medicine Research and Testing Laboratory, urged caution when looking at the data.

  • Daniel Eichner:

    We're just looking at people employed by this one company.

    And so we have got to be careful before extrapolate out to the whole nation on that one. It's a very good study. And so it's really good data. But I think that infection rates are going to vary throughout the country, and they will also vary through different population and demographic areas, for sure.

  • John Yang:

    Some hope antibody testing could eventually lead to so-called immunity passports. Those with immunity would be allowed to end social distancing measures.

    But the World Health Organization said there's not enough evidence for that yet. And, even if there was, Stanford's Hank Greely said, there are ethical questions.

  • Hank Greely:

    In a sense, it almost could lead to a kind of apartheid, where some people are allowed to do some things and others aren't.

    If we had a thoroughgoing immunity certificate system, and it lasted very long, I think there'd be a lot of public discontent, because people would say, look, that's not fair. And they would be right.

  • John Yang:

    So, for now, the advice from most experts is the same: Stay the course until more is known.

    For the "PBS NewsHour," I'm John Yang.

  • Judy Woodruff:

    On Thursday, the FDA did move ahead with its crackdown on antibody tests. Regulators published a list of more than two dozen tests that should no longer be sold in the U.S.

    The FDA says that it will continue to add to the list as it learns more.

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