Medical Examiner

Here’s the Deal With Antibodies and Coronavirus Immunity

Antibodies will probably be key to getting us out of this—in one way or another.

Gloved hands of a doctor are seen pointing at some samples on a table.
A lab scientist works to validate antibody tests of COVID-19 samples from recovered patients in Brooklyn, New York, on Friday. Misha Friedman/Getty Images

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If you are a human being living in the world right now, you are probably wondering some version of: How do we get out of this? As in, how do we figure out how to stop sheltering in place, but also, how do we do that without all catching the novel coronavirus that has already killed more than 20,000 Americans? It’s a question without a real answer, right now, though one promising solution is the idea of antibodies and antibody tests. The tests look for signs that a person has been infected by the virus at some point, which we currently think makes them less likely to get sick again. But, as with everything about the virus, it’s not yet clear what role antibody tests will be able to play in getting us out of this, and it’s even not completely clear how much getting the coronavirus once prevents you from getting it again. Here is everything we currently know about what these tests are and how they can, and can’t, help.

Let’s back up. What is an antibody?

So, as you may have seen, the coronavirus is covered in knobby/spiky things. All coronaviruses have a similar crownlike-if-you-squint spike structure, though we are talking about the novel coronavirus. These spikes allow it to bind to lung cells. Then the virus takes over those cells and makes them do its bidding (which basically entails making a bunch of copies of the virus, thus allowing it to take over the body, America, the world). Antibodies can bind to the coronavirus’s spikes, stopping the virus from latching onto any new cells.

How do I get the anti-coronavirus antibodies?

There are three ways. The most basic (and worst) way to get the antibodies is to get the coronavirus. When a virus invades our cells, our immune system responds by making antibodies against it. When our body has never seen a virus before, this process can take a few days to ramp up, which is why we get sick in the first place.

The second way to get antibodies, the ideal way, is from a vaccine, which we don’t have yet and will not have for a while. Vaccines offer a small, severely weakened or entirely dead dose of a virus; it won’t infect you, but it will prod your immune system into producing antibodies, blueprints that it can swiftly replicate in case you get the actual virus and use to protect you from getting sick.

The end-run way to get the antibodies is from someone who has had the virus and recovered. The antibodies can be transferred via their blood, specifically the plasma portion of their blood, which is the liquid part, basically. Plasma transfusions from recovered patients are one strategy doctors are trying to help patients better fight the virus. As health reporter Nicole Wetsman explains at the Verge, it’s an old technique that was also used during the 1918 flu pandemic, and a potential “stopgap measure” until we have vaccines and better treatments. But some of the drawbacks are that plasma varies from patient to patient, so it’s hard to standardize and figure out what’s reliably working, Wetsman explains, and plasma transfusions in general come with a slew of risks including allergic reactions. We’re still figuring out if the method works at all when it comes to improving recovery.

So once you have the antibodies, you are immune against the virus?

We can’t count on immunity right now. As epidemiologist Marc Lipsitch writes in the New York Times: “Only the first glimmers of data are available about immunity to SARS-CoV-2.”

It does roughly track that if you have the antibodies in your system, the virus will at least have a harder time infecting you. There are two tricky parts: figuring out how long the antibodies hang around after an infection, and what levels of which antibodies—your body creates a few in response to infection—will actually be enough to neutralize the coronavirus. Based on a very small amount of clinical evidence from other coronaviruses, and a little data on antibodies from the novel one, Lipsitch makes an educated guess: If you get the virus and produce antibodies, they “will offer some protection over the medium term—at least a year—and then its effectiveness might decline.”

Wait, but aren’t there people out there who have gotten the novel coronavirus twice, within a short period of time?

Yes, there have been some anecdotal reports. It’s hard to tell if people were truly infected twice or if they never fully recovered in the first place. We just need more data.

So if I’ve been sick with COVID-19 already, should I assume I’m immune, or not?

You could take some personal comfort in Lipsitch’s guess that you likely have some immunity. But as far as your actions go—hanging out with friends, deciding whether to wear a mask, all that—until we have more information, you can’t assume you are immune.

OK. Let’s get to the tests. What’s the deal?

The fantasy of antibody tests is that they might be deployed to help us determine who can go back to work and school and normal social gatherings. Basically, people who have antibodies would get an “immunity passport”—the idea being that because they are known to have the antibodies, the coronavirus won’t make them sick again. It’s a strategy that governments from New York to Italy are considering to help people get back to work.

That sounds very promising!

Sure, but even though the tests can provide a guess at immunity, even a positive result cannot guarantee anything. The science just isn’t there yet, as journalist Neel V. Patel explains in great detail at MIT Technology Review. Beyond the question of how, exactly, immunity works with this new virus, we don’t have an antibody test that’s perfectly accurate, with no false positives or negatives. “We don’t know how to truly predict what proportion of the immunity passports would be issued incorrectly,” Patel writes.

So what are antibody tests actually good for right now?

The short and correct answer is: They are tools to gather more data. What antibody tests are good at doing is telling us the simple fact of who had the virus in the past. And while we can’t yet use them to tell us all that much on an individual level (as in, is it safe for you to go to back to work), they might be extremely useful in understanding what is happening on a population level. (For example, if they show us, hypothetically, that 70 percent of the population has already been exposed, that would change some of our thinking.)

This is why the National Institutes of Health is currently recruiting 10,000 volunteers to take antibody tests. “This study will give us a clearer picture of the true magnitude of the COVID-19 pandemic in the United States,” Anthony Fauci said in a press release. That kind of information, he explained, could help evaluate how well public health measures are working. In that way, antibody tests could be an important tool in opening back up the country … or deciding not to.

There’s one clear way that they could help right now on an individual level: We’ve all been asked to basically assume we have the coronavirus; an antibody test could help clarify our own narratives. At the same time, without more information on immunity, this could be potentially confusing and backfire if people assume they have a level of immunity that they don’t.

The other way that they can help: If you test positive, you can also apply to donate plasma. (It’s also somewhat unknown exactly how helpful this might be, as it’s unclear the extent to which plasma will be helpful, but it’s something.)

OK, so how do I get one?

Antibody tests are done with a sample of blood shipped to a lab. The problem is that there aren’t that many labs doing it right now because tests that look for novel coronavirus antibodies are taking time to get online. (Tests can vary in the exact antibodies they look for and the process by which they do it; figuring out which tests are most reliable for assessing immunity will also take time.) A doctor could help figure out if this would be possible for you. Home testing kits ordered by the British government were found to be wildly unreliable. Small miniaturized blood testing still isn’t doing so hot after the fall of Theranos (well, it never was doing so hot, really). If there’s one lesson we should keep in mind from that about blood testing: We should go slow with our expectations.

For more on the impact of COVID-19, listen to Thursday’s What Next.