We need a new test to know who has had - and recovered from - the coronavirus

George Miller is the John F. Enders professor of pediatrics, and professor of epidemiology, at the Yale School of Public Health.

Anxious citizens, medical professionals and elected officials all want to know why the federal government has been so slow to deliver the tests that detect who is and isn’t infected with the novel coronavirus. Less prominent in the public discussion, yet also urgently needed, are complementary efforts to develop and deploy tests for coronavirus antibodies, proteins produced in response to exposure to the virus, which help fight it off.

It's obvious why we'd want tests to know who is infected, and therefore infectious: Patients who test positive ought to be sequestered, whether they are at home or at the hospital, and medical professionals who come in contact with them ought to be wearing the maximum protective gear available.

An antibody test would, similarly, help to identify people who have been infected (although, since it takes time for antibodies to develop, it is not recommended as a diagnostic test, used alone). But crucially, such a test would pinpoint those who had covid-19 but mounted an immune response and recovered without needing hospitalization. Given what we know about how the body responds to viruses, those people would be unlikely to contract the disease again, at least for a significant period. Deploying the antibody tests, in tandem with those that identify infections, would therefore help us sort out who can safely reenter the workplace - and rejoin society more generally.

Yet while it's been mentioned in reports and discussed by experts, including in a guide to fighting the coronavirus by Scott Gottlieb, a former Food and Drug Administration commissioner under President Trump, antibody tests remain an underappreciated tool to ensuring that hospitals, businesses and public spaces remain safe - or, in some cases, return to normal operation. Governors aren't demanding antibody tests with the same vigor that they're asking for PCR tests, yet they should be.

Such tests already exist mainly in experimental form. The pharmaceutical company United Biomedical, for example, donated enough kits to San Miguel County, in Colorado, to test the entire county's residents. No antibody tests, however, have been authorized by the Food and Drug Administration - although the FDA is permitting their use if that fact is disclosed, along with the tests' limitations as a pure diagnostic tool. Still, without FDA approval, many institutions are hesitant to deploy them. United Biomedical has submitted its test for authorization, and other companies, too, are scrambling to create their own, but for all intents and purposes antibody tests are not a tool in the U.S. public-health arsenal yet. (China and South Korea have made more use of them.)

Once they are in ample supply, a good place to start antibody testing would be hospitals, such as the one in Cambridge, Massachusetts, where my son works as a pulmonologist and critical care doctor. Hospitals could institute regular, across-the-board antibody screening for all health care workers who have intimate contact with patients. If the test comes back positive, the worker gets a follow-up test from a PCR kit. Workers who get positive PCR results would be sent home to self-quarantine. But a negative PCR result together with a positive antibody test would mean that the worker has been exposed, has recovered and has developed an immune response to the virus - extraordinarily important information.

Close testing and continued monitoring would also help to determine the extent of immunity that develops in response to exposure: We don't know yet if it is permanent, or of shorter duration. (Exposure to some other SARS viruses produces immunity lasting a year or longer, we know.) Nonetheless, the more we know about the antibody status of our health care workforce, the healthier that workforce can remain for the duration of the crisis. This approach could subsequently be extended to the general population; the immune could in some cases go back to work.

Antibody tests can help in the coronavirus fight in other ways, too. Widespread testing for antibodies would be of great use to health care workers attempting to trace the contacts of infected patients - a process that the United States has barely begun, yet which was used to significant effect in South Korea (although that country relied mainly on PCR testing). As epidemiologists worked their way back from hospitalized covid-19 patients into communities, to see whom they crossed paths with, antibody testing would help identify the people most at risk. Those people would be monitored far more closely than people possessing antibodies, improving the efficiency of the tracking system.

An antibody test could also help solve one of the greatest mysteries of covid-19, one that dovetails with my particular interests as a pediatrician who has also studied viruses and infectious diseases for nearly 60 years: Why don't the severe symptoms show up in kids? Is it because they've been exposed, developed antibodies and become immune? Or because they don't get infected in the first place? Answering these questions requires testing both for antibodies and for infections. On a more practical level, the tests could help children's' lives, too, return more speedily to normal: Children who test positive for antibodies might be allowed slowly back into the classroom - although this would raise issues of equity for those who must remain at home.

Finally, antibody tests are a crucial step on the road to developing a vaccine. They cannot only identify immune individuals, but help to narrow down which specific types of antibodies confer protection. Any successful vaccine would be expected to induce the production of those particular antibodies, which inhibit the ability of the virus to infect host cells. Then, once a vaccine exists, antibody tests can help identify people who lack the protective antibodies and therefore need to be inoculated.

Covid-19 is still spreading rapidly throughout the United States, and antibody tests remain an underappreciated weapon in our fight to stop it. Armed with such tests, we can provide the public with much more specific information about their own susceptibility, possibly permit immune individuals to return to work and help people make more informed decisions about when and whether to loosen restrictions on their social activities. That such tests will guide us toward the goal of a vaccine is the ultimate argument for developing and distributing them as quickly as possible.

Originally published by The Washington Post

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