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Will antibody testing help ease lockdown restrictions?

As scientists rush to find a vaccine that could end the global pandemic, some cities and states in the U.S. are relying on antibody testing to get a better picture of how the virus has spread and how many people it has infected. Others are pinning their hopes on the idea that antibodies could mean immunity from COVID-19. ProPublica reporter Caroline Chen joins Karina Mitchell to discuss.

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  • Karina Mitchell:

    Antibody testing for COVID-19 is becoming more readily available, but there are still multiple unknowns about what the test results actually mean when it comes to public health.

    I spoke recently with ProPublica health reporter Caroline Chen to help explain some of the confusion.

  • Karina Mitchell:

    Caroline, thanks so much for joining us. There's been such an intense focus on antibody tests both here in the US and overseas, but not without controversy, and some of the methodologies that are used in the studies have been questioned as well for bias in sort of other elements that can, you know, sort of sway results.

    So how reliable are these tests and how dangerous is a false positive?

  • Caroline Chen:

    So there really questions you ask right there. So let me break this down a little bit here.

    So antibody studies that are now being conducted nationwide at state levels and even at county levels are really, really important because they can actually answer many questions.

    But the most common type of study that's being done right now is to ask this very basic question, which is what percentage of this population has been infected? And what they are doing is that they're supposed to look at a random sample of a given population, let's say, in this specific county or in this specific state. And by taking a random selection of the population and looking in their blood to see if they had antibodies, you can get a scent, a sense of what portion of that population has been infected. And that's really important because to date, as we know in the U.S., there has been a shortage of the diagnostic tests.

    And so only really, you know, people who have had really severe symptoms, who have met, who have gone to the hospital, have managed to get tested. So we know that the case counts are probably undercount, but we don't know how much of an undercount. So that's where these studies can help to fill in our understanding.

    So you mentioned that there's been some controversy about these and they're kind of maybe two big pieces of this. So the first thing you said is accuracy of the tests. Right. So if the tests aren't super accurate, then, of course, that can skew the numbers. Everybody understands that part.

    The other trickier part is what you mentioned, which is bias. And what scientists mean when they say bias is that they mean that they're worried that the sample that was tested wasn't totally random. And there are many different ways you can recruit participants.

    But basically the concern is if you're saying you volunteer, whether I recruited by Facebook ad or whether I'm just posting something on the Internet and they email me if you want to participate, that the fear is that people who think that they have been affected, who say, oh, I had a flu back in February or I had a cough back in February, they're more motivated to participate. Whereas if I say, oh, I've been totally healthy this whole time, I don't think I had the Corona virus, I'm going to not want to participate. And that could skew the numbers.

    So the ideal way to do this type of study is to have a database of addresses and then to randomly pick addresses and then invite people to participate.

  • Karina Mitchell:

    And the results of who has the antibody and who doesn't. There is a vast range of differences. I've seen numbers as low as 2 percent all the way up to 30 percent.

    So how do those numbers compare to so-called herd immunity and the metric that they're looking for that?

  • Caroline Chen:

    I think these numbers have come out, you know, whether it is down at 2 percent or whether it is up at 30 percent, which was in Chelsea, Massachusetts.

    I think a lot of the headlines people are seeing go along the lines of, you know, there are far more infections in our community than were previously thought. And I think that that is one that is true.

    So then some people start to say, so are we actually close to herd immunity and herd immunity is the idea that when the vast majority of the population is infected, that the virus will not have enough new potential carriers to infect and so will stop circulating?

    Now, I think it's really helpful. Just keep the numbers in your mind. So I've asked a lot of scientists how many people need to be infected for there to be herd immunity. And I've got a range of answers. But the lowest number I've heard is 60 percent. Most people say 70 to 80 percent. I've heard as high as 90 percent.

    The reason why that's not a fixed number is because it depends on a number of different factors, like how contagious exactly the Coronavirus is. And also this still open question of if you have been infected, are you then immune forever like the chicken pox or does your immunity actually start to wane over time? A

    ll the studies that have come out in the US. Regionally, we're nowhere near herd immunity. So unfortunately, I think the only other way to get to herd immunity is via a vaccine. And that's also some ways away.

  • Karina Mitchell:

    So much of this is uncharted territory. When do you think it will be possible, taking all these snapshots to put them together and get some sort of sense of where we actually stand as a country.

    How many people have the antibodies and when we can start sort of thinking about as a whole country going back to work and feeling much safer?

  • Caroline Chen:

    I think that actually we're going to be able to get a good sense regionally and sort of maybe added potentially at a county level, you know, even within weeks, because there are some counties like Miami-Dade County that are already doing this on a weekly basis.

    And in New York state, where they are already updating their numbers because they are doing this on a weekly basis. So I think, you know, you may not have a perfect picture already, but you are already starting to have a picture that is becoming more and more focus week by week as you do this.

    And I think that's very hopeful because we can get more and more information as we go, even if it's not yet perfect. And learning the proportion of people who are infected in the population is so important for us to better understand the coronavirus and also to get a sense of how fast is this disease spreading.

    But these are all important pieces of information, both for scientists to understand the virus and for politicians to get a sense of what's happening in their city as they make decisions on things like should we reopen? How fast should we reopen? Are the social distancing measures helping? And also, they'll start to do these studies in select populations, like what portion of health care workers or frontline workers like grocery store workers are infected?

    Like all these pieces of information start to help build a better picture regionally, statewide, county wide, and then maybe put them together to get a picture of the nation.

  • Karina Mitchell:

    Caroline Chen, ProPublica, thank you so much.

  • Caroline Chen:

    Thank you for having me.

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