The State of COVID Antibody Tests

There have been a series of promised easy fixes for the coronavirus pandemic: hydroxychloroquine, convalescent plasma, even ultraviolet light and disinfectants. Although not a cure, a lot of hope was invested in a quick blood test which could determine if a person had antibodies for the virus, on the assumption that these antibodies would convey what President Donald Trump called “wonderful, beautiful immunity. Several tests are available, but their reliability is questionable. Also not yet determined is how long immunity, once achieved, will last.  

Some people have become impatient and have called for an end to all safety measures, to sacrifice possibly millions of people in the hope of achieving herd immunity – the same strategy used in Sweden earlier this year. This idea is promoted by many Americans, even though that strategy cost Sweden almost as large a fraction of its population as have died in the U.S., and even though the average Swede is much healthier than the average American.   

Dr. Jennifer Rakeman, a member of New York City’s Public Health Laboratory, told the Associated Press, “There was definitely a lot of wishful thinking that there was going to be a magical test that was going to save us all, but we’re not there yet.  

Even if a test could confirm a person’s antibody status at the moment, how long immunity will last is unknown. One early study suggested it could fade within a few days, while later ones show the presence of antibodies for months after recovering from a coronavirus infection. Normally, the duration of immunity after an illness is learned only after years of study. Right now, animal studies are being done of more than one test, but they are not yet ready for human trials.  

Some testing laboratories are marketing antibody tests as a way to determine whether a worker can return to the workplace or a child can safely go to school, but the Centers for Disease Control and Prevention and the American Medical Association caution strongly against using a test to make such a decision. Antibody tests are more useful for studying populations than for deciding if any given person is immune.  

Because of the desire for an antibody test to use immediately, the FDA did not apply its usual testing requirements, but authorized 170 different tests to go to market with very few trials, which some doctors referred to disparagingly as a Wild West approach. Hundreds of millions of tests were manufactured, some used within the U.S. and some being sent overseas as a contribution to fighting the pandemic, which Trump referred to as “fantastic progress” against the disease. There have been reports, however, of EU authorities discarding millions of tests, having declared them defective. Some suspected the administration of dumping undesirable tests onto other countries to avoid their being used in the U.S.  

The casual acceptance of tests was reined in during May. Marc Jenkins of the University of Minnesota told AP, “Even the research community can’t really tell you what the result means,” and advised against paying for an antibody test unless a physician specifically recommended it.  

The CDC calls on all people, even those who have recovered from a case of COVID and who have had a blood test that shows the presence of antibodies, to observe the precautions which they have been urging from the beginning: social distance, masks, hand washing, staying home whenever possible.  

John M. Burt