Short Wave - We Don't Know Enough About Coronavirus Immunity

Episode Date: June 16, 2020

Does getting the coronavirus once make you immune to it or could you get it again? Many are looking to antibody tests for answers. The logic is: if I have antibodies for the coronavirus, I must be immune.Well, turns out ... it's complicated, as Katherine Wu writes for the Smithsonian Magazine. We invited her onto the show to explain. Between episodes, you can catch up with Maddie on Twitter @maddie_sofia. Plus, we always want to hear what's on your mind — coronavirus or otherwise. Tell us by emailing [e-mail]. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

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Just go ahead and follow or subscribe. You're listening to Shortwave from NPR. Maddie Safai here. and today we are talking about immunity. Everyone wants to know, especially now that many states around the U.S. have started to open up, does getting the coronavirus once make you immune to it? Or could you get it again? And people are looking for the answer in antibody tests,

tests that can tell you if you've had coronavirus. A lot of the antibody tests that we're seeing come back either positive or negative. And that makes immunity also seem like. like it's positive or negative. Cut and dry, right? Not so much. I think the better way to think about immunity is as a continuum or a spectrum where your body has a reaction somewhere along this really long axis. And at one end, it's a really...

Our immune system is beautifully complex. It takes many different molecules and cells to fight off infection. Catherine Wu, much like me, is a microbiologist and a big fan of the immune system. She recently wrote a piece for the Smithsonian magazine about just this, why immunity is so tricky. A lot of people end up using the word immunity when they actually mean a bunch of different things. Every infection is different, and every person's immune response is different. So when I say I have immunity against something, it really just means that my body is a reaction. to the presence of something that is trying to infect me, not how well it does it.

So today on the show, a beginner's guide to immunity and what that means for how we understand those antibody results. As Catherine Wu tells us, for the coronavirus, it's complicated. Okay, so Catherine, let's start off by talking about some of the basics of our immune system. In your piece, you talk about how an immune response requires a symphony of cells, which I love, by the way. And generally speaking, our immune system responds to pathogens like the coronavirus in two waves. Walk me through that first wave. Yeah, great. So the first wave that really happens is what's called the innate immune response. And basically, in this wave of cells, there's this very quick and general response. If you kind of compare the immune system to like an army, these

or maybe kind of the guerrilla fighters, this battalion of soldiers that are just sort of taught to recognize anything that doesn't look like you. Sometimes when immunologists talk about innate immunity, they talk about cells that recognize the difference between self and non-self. So if the immune system has grown up around all of your organs and tissues, it can say, hey, this is a heart cell that belongs to Maddie. I'm not going to attack that because this, in this context, in Maddie's body, that's self. But anything that doesn't, have the sort of signatures that say, this is a cell that belongs to the body that I have grown up in. It'll say that's foreign and I need to attack that and get rid of it. This can actually be

anything from a pathogen that doesn't even look like a human cell to a cancer cell, which has come out of a cell in your body, but just looks strange or unusual enough that it's no longer recognizable. Yeah, yeah. And so, and then there's the second wave of immunity, right? So this is adaptive immunity? Right. So the second wave is actually really important to frame as a second wave because it does literally come second. It's a lot slower, but it's a lot more specific. We're talking about something that needs a lot of time to basically learn and tailor make a response that's going to root out very specific pathogens and target them. These are kind of like the snipers or assassins if we're kind of going back to our, our men.

militarized or army metaphor. And if that pathogen tries to infect you again, you'll mount that same adaptive immune response. If that pathogen comes around a second time, it won't be quite as slow. It'll be just as specific, but it'll be more powerful and faster. And ideally what happens is you won't get as sick. That pathogen might infect you to some extent or possibly not even at all, but your immune system will have already been trained by a past exposure and be really good at fighting that pathogen off the second time. Yeah, yeah. And this is where, generally speaking, antibodies really make their moves, right? Yeah, so antibodies are these Y-shaped proteins that are turned out by these cells called B cells. And B cells are part of this adaptive immune response,

that second wave that is really specific but sort of slow to arrive. And what B cells do is they are basically antibody factories. They turn out these proteins that are able to do all sorts of disease fighting functions. So a lot of people, when they hear about antibodies now, the sort of general description for antibodies is that these are proteins that are able to kind of latch onto the surface of a pathogen like the coronavirus and stop it from infecting cells. If a virus can't get into a cell, for instance, it can't make more of itself. It can't actually do much damage to your body. Right, right.

But let's talk about antibodies and antibody tests. We're talking a lot about using those now as a way to determine whether somebody has had coronavirus in the past, and if that means they're immune from getting it again. Tell me a little bit about the limitations of those antibody tests. Yeah, so I'm really glad you phrased it that way because the sort of two metrics that you're talking about are actually separate. So with a good antibody test, it can definitely tell you whether or not you have had an infection in the past. But the way I sort of like to think about it is antibody tests can tell us a lot about our past, whether we've previously had an infection. But they can't necessarily tell us a lot about our future, whether we're going to be protected from that same infection. again. And this is the distinction that I think we really need to draw for people. Right. So this idea that people can get an

antibody test, test positive for coronavirus, and feel like, well, I can't get it again is kind of the wrong way to think about it. Yeah, I think that's right. And I do want to leave room for the idea that it may be the case that that turns out to be true, that people can't get reinfected if they have antibodies in their blood. That's definitely still possible. But it's not something we know yet. And, you know, I think it's better for now to sort of err on the side of caution because if people assume that they are protected and they aren't, they might feel emboldened to go out and not wear face coverings as often or not wash their hands as frequently. And that could put them in danger as well as the people around them in danger. So for now, it's probably best to assume that, you know,

there's a very, very good chance that we won't be protected if we do have antibodies in our system. Another thing to possibly add here is that, you know, there is precedent for this. We know of other viruses, other pathogens for which people do generate an antibody response to them, but that doesn't actually serve as a good proxy for whether or not they'll get infected again. Right, right. And that's kind of the long term, right? So it's really hard for us at this point to understand that because the virus is so new. But what about what we know now, Catherine, about immunity in the short term for coronavirus because we have a little bit of data on it, right? Yeah, that's a great question. And I absolutely don't want to give anyone the impression

that we're all doomed to just have the same disease over and over and over and over again. We are still working towards, you know, having an effective vaccine and people generally, you know, safely assuming that we're going to have some protection against the coronavirus for at least the short term. I think it's important to mention here that, you know, there have been other coronaviruses that have infected the human population before. Some of the most commonly mentioned ones are actually coronaviruses that cause, you know, common cold like symptoms. And I think, you know, what researchers have figured out so far is that we actually do develop

immunity against those coronaviruses. They don't last too long. It might be on the scale of a few months. In the case of some coronaviruses, it could be up to a couple years. But I think, you know, given that we're operating in the short term here, we're like six months into this current coronavirus pandemic, I think it's probably safe to assume based on what we've seen in a bunch of studies that people who have been infected once probably aren't going to get infected again anytime soon. And people should take comfort in that. Yeah. So I'm kind of interested in this in general, Catherine.

Why did you decide to write this piece? That's a very good question. And I think this actually gets back to something that we started our conversation with, which is you sort of evoking the idea that immunity isn't binary. I think I kept hearing people say, I'm getting an antibody test next week. I'm really, really hoping it comes back positive. And I think that's one difficult thing about these types of tests where we're using, like, a molecular marker in the body as a proxy for something really complicated, in part because there are so many things at work, there are so many factors that can determine how your body responds to a pathogen that I just wanted to make sure people understood that they can have immune responses

that are giving them partial protection, and that's still super important for, you know, herd immunity and keeping our population as a whole safe. They can be super well protected, and that's great, but that might not be true of the person next to them. So I think this is important for people to think about on an individual level in terms of we can't predict how you are going to respond to this particular virus, but it's also important for the population level that we can't make any assumptions about what's going to happen to the people around us. All right, Catherine Wu, I appreciate you.

Thank you for bringing your love for immunology to shortwave. It's very nice. Thank you. It was a pleasure to speak with you. I'm a huge shortwave fan, and this is, The honor of my life. All right, Catherine, I'll talk to you later. All right.

This episode was produced by Rebecca Ramirez and edited by Viet Le. Britt Hansen checked the facts. I'm Maddie Safia. Thanks for listening to Shortwave from NPR. For James McBride, racism in this country has been a disease. It's been the cancer that has just been killing us. And now we want to address the problem. I mean, you can't address the cancer until you know you have it.

And these people are seen. the cancer. Author James McBride on protests, a pandemic, and his new book. Listen to It's Been a Minute from NPR.