Monday, April 20, 2020

Are Immunity Passports In Our Future?

Here in the midst of the COVID-19 crisis, many of us are starting to wonder how it's going to end.  Just last Friday, Texas Governor Greg Abbott announced plans to lift certain restrictions related to the pandemic.  Regardless of what governments do, the big question people have is not so much what's happening to the economy in general, but this:  "When can I safely resume my normal way of life?" 

Some people never stopped working—notably many healthcare workers, first responders, and employees of essential businesses such as grocery stores.  But they have kept working while trying to protect themselves from the virus, and that doesn't always succeed.  For example, numerous meat-packing plants across the U. S. have shut down because of the spread of COVID-19 among their employees, despite the strict microbiological protocols that such packing plants have to observe. 

Wouldn't it be nice if there was a simple, cheap, fast blood test to tell if you have the SARS-CoV-2 virus that causes COVID-19? 

Lots of pharmaceutical companies around the world have rushed into production just such devices, referred to as point-of-care antibody tests.  Many of these are what the specialists call "lateral-flow assays."  You get a drop of blood from the patient and put it on an enclosed test strip.  As the serum flows along the strip it encounters some stuff that changes color if the blood sample has the specific antibodies that the virus in question provokes the body to make.  And a final strip turns color to verify that the stuff got that far, as a reliability check.  The whole thing takes only 15 minutes or so, and the tests can be mass-produced for as little as $3 each.

Already, governments and institutions around the world are using these antibody tests for finding out who has antibodies.  They are not intended to be used to diagnose COVID-19, however.  It takes your system a week or longer after infection to develop enough antibodies to show up on an antibody test.  So you can be walking around with COVID-19 and infecting other people, and still test negative on an antibody test.  The gold standard for having an active infection is still the laboratory-based polymerase-chain-reaction (PCR) test, done typically with a nose-swab sample that is sent to a high-tech lab, although there are point-of-care versions of PCR tests now available as well. 

But the test that is generating the most interest is the antibody test.  Presumably, a person with enough antibodies against COVID-19 is immune, although the truth of that assumption is actually still a research question that is currently being investigated.  As if that wasn't complicated enough, there are neutralizing antibodies, which confer long-lasting immunity, and binding antibodies, which just fight short-term infections.  Most of the point-of-care antibody tests detect only the binding antibodies, which indicate that you've been dealing with the virus recently.  Most people, but not all, go on to develop the neutralizing antibodies that confer immunity, but for how long, nobody knows yet.

Okay, so say I'm a manager desperate to get my factory back into production, and somebody comes along and offers me an antibody test.  I will be strongly tempted to require all of my workers and prospective employees to take the test, and only allow in the ones who test that they are immune.  Right now, that might not be a large percentage, but as time goes on and the hoped-for "herd immunity" develops, such a testing policy might be very tempting.  In effect, you'd have to have an immunity passport in order to go back to work.

Already, many health care institutions are planning to administer antibody tests, with the assumption that anyone who tests positive can't get COVID-19, or is at least much less likely to catch it, and so they might be the people you put on the front lines dealing with COVID-19 patients, reserving your non-immune staff to safer duties.

And let's get personal here.  What about teachers or others who deal with large numbers of people in close proximity?  When I was hired at Texas State University, I had to show that I passed a TB test.  That was to make sure I didn't have tuberculosis, which can be a chronic asymptomatic disease that can nevertheless be spread by otherwise apparently healthy people. 

With COVID-19, it's sort of the opposite problem.  Without a vaccine (and most experts think that's at least a year away), the only way you can safely start being in proximity with strangers on a routine basis is if most of the other people around you can't get COVID-19.  That's what herd immunity means, and we don't really know how far away from that we are, without widespread antibody testing of representative samples of the population, both apparently healthy and otherwise.

That's probably the best current use of antibody tests:  to monitor the average state of immunity in a geographic area with random sampling of both healthy and sick people.  That way, even if the tests aren't 100% accurate (and many of them fall short of that), you can factor the errors into statistics and still arrive at a pretty good aggregate number, and it doesn't matter if the odd result here or there is wrong.  In particular, it won't condemn to continued unemployment a person who has really had COVID-19 but the antibody test wrongly says he or she hasn't had it. 

A perverse situation might arise in which those of us, especially ones over 60, who have gone to extraordinary lengths to avoid catching the stuff, end up being sort of inverse Typhoid Marys.  Our employers might say, "Look here, I'll take back people who have had it and can't catch it, but you susceptible folks, you'd better stay away for a while longer until the herd immunity gets so high that it's unlikely you'll catch it regardless."  Maybe not every employer will think that way, but some of them will.

At this point, it looks like the antibody tests are simply not reliable enough to do such specifically targeted testing, especially if the results can mean continued unemployment or worse.  But look for problems to crop up along these lines, and where such problems show up, lawyers can't be far behind.

Sources:  I referred to an article on the website of the Journal of the American Medical Association by Jennifer Abbasi at  The meat-packer shutdown is described at

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