I tested positive for coronavirus antibodies — what now?

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.

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 United Kingdom’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 in his early 60s, 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. (President Trump has bragged that after getting covid-19 he is now immune .)

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 allowed those who can prove their post-covid status to 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 coronavirus tests — either for the virus or the antibodies. One of the few published studies, carried out by British academics and the Behavioral 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.

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 Great Britain, where I live, 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-19, 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 such as 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 uses only 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 a company that claims 100 percent sensitive — meaning everyone who has had the virus will get picked up — and 99.6 percent specific, meaning only rarely will something other than the coronavirus trigger a positive reaction. (Although independent tests carried out by the British 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.

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 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 some time.

“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. Some worrying data suggest that antibody levels drop off within a few months of infection. 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, coronavirus 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 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.

Immunity passports?

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?

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.

Natalie Kofler, a molecular biologist and bioethicist at Harvard Medical School, is not a fan, partly because she says immunity passports 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.

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.

David Adam is a freelance science journalist in the UK who now eats far fewer chopped chili peppers. This report was first published by Knowable Magazine.

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