I tested positive for Covid-19 antibodies — what now?

It’s more difficult to squeeze blood from a hole in your finger than you might think — I milked a cow once, and the technique is much the same. I’m just grateful I only needed about a milliliter.

I mailed off the sample to a private lab in London at the beginning of June, and a week later the verdict dropped into my inbox. “Test: SARS-CoV-2 IgG. Results: POSITIVE.” (It really was red.) The accompanying text spelled it out: “You can be highly confident that you have been infected by the virus.”

At this point in an article, any responsible journalist would list the caveats: the likelihood of a false positive result, that scientists don’t know how long the antibodies detected by the test will last, and — most important — that we don’t yet know whether such a result indicates someone is protected from reinfection. And we’ll get to those.

But first, a little honesty: My first reaction was to whoop with joy, crack open a beer and call my elderly parents to arrange to see them for the first time since Christmas.

I’ve been reporting on this pandemic for months. I have spoken to myriad experts, listened to endless government briefings, read stacks of scientific reports. When it comes to Covid-19, I can tell the known unknowns from the unknown unknowns. Yet I still joke with people I meet about how my antibody status makes me bulletproof. (And the subject always comes up. I think we can safely repurpose the old joke about Mensa: How do you know if someone you meet has had Covid-19? They will tell you.)

So I was relieved to see others who seemed to react the same way I did. Matthew Cobb, a professor of zoology, no less, at the UK’s University of Manchester, admitted on Twitter that he was disappointed when his own antibody test came back negative. “I know there is no reliable evidence that if you’ve had it you won’t get it again,” he later told me. “Despite that knowledge, which I can hold very clearly in my rational brain, I was clinging to the hope that I would have been protected.”

Importantly, Cobb, who is 63, says a positive test would not have changed his behavior. But he thinks it would have made him less apprehensive. And there’s the rub: As more and more people do find out they have antibodies after being infected previously, then how they react, think and behave — or don’t — will become a major new factor in the world’s attempts to control the spread.

Already, some countries are looking at “immunity passports,” which might allow those who test positive for antibodies to return to work earlier, or to travel with fewer restrictions; in Brazil, the country’s famed Fernando de Noronha islands recently announced that those who can prove their post-Covid status may now visit. People are even reportedly using their antibody status as a way to boost their success on dating websites.

There’s surprisingly little information on the psychology of how people react to being told results from Covid-19 tests — either for the virus or the antibodies. One of the few published studies, carried out by UK academics and the Behavioural Insights Team (a former British government unit now spun off into a company), found that about 10 percent of people who were asked to imagine a positive antibody test said they believed that would leave them no chance of catching the virus again. When the researchers used the word “immunity” to describe the test or the results, that figure doubled to almost 20 percent.

Theresa Marteau, a psychologist at the University of Cambridge who worked on the study, says more research is needed — quickly — on how people who receive positive antibody tests go on to change their behavior. Her research did suggest that those who receive a positive antibody test might wash their hands less often. And a related survey of some 6,000 people, most of whom hadn’t had tests, found that those who believed they had been infected by the virus said they were less likely to follow social distancing guidelines.

First reactions and intentions are useful information, Marteau says, because they help behavioral scientists work out the best way to communicate what a positive antibody test truly means to the increasing number of people who will request and receive these tests. But these survey results should be interpreted with caution, she adds: “We know there’s such a difference between what people say they are going to do in a hypothetical context, and what they actually do.”

Take me: Although I told my parents I was safe to visit, after some consideration we agreed it was a bad idea and I stayed home.

Testing positive for uncertainty

I requested my own antibody test out of curiosity. Sickened back in April, my symptoms were mostly mild — coughing and muscle ache —and because I didn’t have an elevated temperature, I self-isolated and slept in the spare bedroom out of an abundance of caution. But I told myself it wasn’t the coronavirus. It was only when I woke up one morning with no sense of smell or taste, and amused myself for a couple of days munching through jars of chopped chili peppers with impunity, that I started to wonder.

In the UK, availability of antibody tests and information on their reliability have fluctuated, with kits made available at pharmacies and then withdrawn. Initially, I signed up as a donor for a National Health Service trial that took blood plasma from those who had experienced symptoms and used it to treat Covid-19 patients. That way, I figured I would discover my antibody status, and also, if it was positive, do something helpful with it. I spent a fascinating hour watching my blood be removed and separated and then the red bit put back into my arm. They took the clear bag of plasma away and tested it.

By then, I was pretty convinced I’d had Covid, so it came as a surprise when a letter arrived saying thanks but no thanks: “When we tested the levels of Covid-19 antibodies in your blood we discovered that they were below what is currently thought to be necessary to treat patients.” I was surprised and, just like Cobb, disappointed. But also puzzled. The letter did not say they didn’t find antibodies, just that they didn’t find enough. So — did I have any or not? Had I had the virus or not?

It turns out that the trial couldn’t tell me. Antibody levels are typically measured as titer: a unit based on the quantity needed to do things like suppress virus activity in cell cultures or show up on plate-based tests. To make sure it has the highest chance of success, the NHS trial only uses samples from donors that have a titer 100-fold greater than that. And their letter didn’t tell me what my exact titer was, just that it wasn’t enough. About half the people who have definitely had the virus would get similar results to mine.

I needed a different test, one that would report a lower titer, to get the yes/no answer I sought. I got one from Abbott that the company claims is 100 percent sensitive — meaning everyone who has had the virus will get picked up — and 99.6 percent specific, meaning only very rarely will something other than the SARS-CoV-2 virus trigger a positive reaction. (Independent tests carried out by the UK’s public health agency found that the test isn’t as sensitive as advertised and would miss 6 percent of positive cases.) My wife, who showed milder symptoms than I did, also tested positive for the antibodies, which is corroboration enough to convince me that my positive result was correct.

But what does that mean? This is where things get fuzzier. Encouragingly, it’s highly likely that catching the virus once does reduce the chance that someone would get infected again, says Al Edwards, a former immunologist who now works as a pharmaceutical engineer at the UK’s University of Reading. But immunology itself, he says, “isn’t very good at predicting these things.” Only careful studies of large numbers of people to check how many are infected twice will allow immunologists to say with any confidence that a positive antibody test offers reassurance, he says. In other words, if there is lasting protection, then we won’t know that for sure until it, well, lasts.

And that will take a while. “What we’re aiming for is to have multiple independent studies, which have enough data to be confident. And then we can build a consensus,” Edwards says. “And the difficult thing is that we need to make decisions quickly. So, there’s this massive urgency, but those studies are slow and painstaking and difficult.” That’s not very helpful for policymakers who are asking scientists for the evidence to help them make decisions in real time.

As a shortcut, researchers are tracking antibody levels in people over shorter periods of time. And many people were dismayed by preliminary data from more than 60 patients and healthcare workers in London showing that antibody levels in their blood declined over three months. But though that sounds alarming, immunologists — again — don’t know what it means. It’s certainly not clear what impact that would have on someone’s reinfection risk.

For one thing, Covid-19 antibody tests are designed to measure if someone’s been exposed to the virus, not to answer questions about their future immunity. Some of the tests, including the Abbott one I got, don’t even probe for the types of Covid antibodies whose ability to help fight the virus is the most established. And as Edwards and others point out, antibodies are only one measure of the immune response. Some studies have found elevated levels of another immune defender, protective T cells, in Covid-19 patients, even if no antibodies are present. And the presence of “memory” immune cells could allow the body to ramp up a quick response if someone was exposed again.

Let’s assume that infection does offer some immunity and that we can identify such protected individuals with a reliable test. What then? Are immunity passports a good idea? Already, countries such as Estonia are planning such a scheme as a way to get people back to work, says Natalie Kofler, a molecular biologist and bioethicist at Harvard Medical School. Kofler is not a fan, partly because she says they could worsen existing inequality in society, and partly because they pander to the needs of individuals over the idea of collective action for the greater good. “To argue for immunity passports, you have to argue for individualism,” she says.

It’s easy to see how such demands might take hold. Just look at footage of people yelling about their “freedoms” when simply asked to wear a mask in a supermarket.

Still, I did quite like the idea of an immunity T-shirt, if not a passport. But that — I told myself and Kofler — was to reassure other people that I was no threat to them. Kofler saw straight through me. “To not feel the discomfort of people being afraid of coming too close to you could still be seen as a self-serving motivation,” she says. She’s right. I liked the idea of gliding freely through the world, to sit in a pub and not bother with a mask. To put the crisis in the past tense on a personal level.

Marteau, for one, offers a sympathetic ear. “There are all sorts of emotions attached to different viral statuses and our feelings don’t always align with our cognition,” she says. “Even having all the information and knowing about the uncertainties does not stop one from feeling somehow in a different state to others.” That’s certainly how I feel.

Don’t think too badly of me. I’m very much aware of my newfound antibody privilege, and I’m trying to expose and explore it. Because if millions of other people start to feel the way I do, then we could have yet another problem to add to the mess that 2020 has already gifted us.

This article is part of Reset: The Science of Crisis & Recovery, an ongoing series exploring how the world is navigating the coronavirus pandemic, its consequences and the way forward. Reset is supported by a grant from the Alfred P. Sloan Foundation.