Covid-19 may be here for a long time. As work and activities begin to resume, there will continue to be risk and many new precautions. But for people who were exposed to the virus and recovered, the risk is much lower. Knowing if you had the infection and recovered will soon take on added importance.
There are two main types of immunity to an infection. Innate immunity comes from circulating cells that attack any invader the body views as foreign. Adaptive immunity is specific to the pathogen presented. Through adaptive response, immune cells are programmed to secrete antibodies that are primed to target a viral invader.
These antibodies can circulate for a long time and make a person immune to reinfection. Whether people infected with Covid-19 develop lasting immunity hasn’t been established with certainty. But it’s clear that infection triggers a strong immune response and the production of neutralizing antibodies. There’s still a lot to learn. But if this virus behaves like others, including other coronaviruses, there’s reason to believe that these antibodies are protective at least for a year or so.
Evidence suggests that even asymptomatic people infected with Covid mount a robust antibody response. In most parts of the country, exposure may be low, perhaps 5% of the population nationally. But in hot spots like New York, New Orleans and Detroit, the odds of being exposed are much higher. Antibody surveys conducted in New York City in April showed that about 21% of New Yorkers may already have antibodies to Covid-19. By the time the city’s epidemic runs its course through June that number could reach as much as one-third. But how to use evidence of immunity has been a subject of debate.
First, on whether patients can trust the tests: Determining whether you’ve been exposed to Covid-19 and developed some immunity involves serology tests that screen for the neutralizing antibodies that the body produces in response to the infection. Initially, the Food and Drug Administration allowed these serology tests to enter the U.S. without review because they weren’t classified as diagnostic. Dozens of tests from China flooded the market, many of questionable quality and accuracy.
Recently, reputable manufacturers entered the market with good tests that they asked FDA to evaluate. The National Cancer Institute has been reviewing these tests to confirm accuracy, and sharing the results. Because there are now reliable tests authorized by FDA, such as the blood test from Quest or the panels from Roche and Abbott, last week the agency gave other tests 10 days to submit data proving their accuracy or face removal from the market.
While all of these tests can still generate false positives—a finding that you have the antibodies when you don’t—that risk can be sharply reduced by repeating the test if it comes back positive. The predictive value of two consecutive positive tests is high enough that you can be confident antibodies are present.
There are concerns about privacy. In Chile, Germany and the U.K., researchers and politicians have floated the concept of giving residents “immunity passports” that would allow people who have recovered from Covid-19, and have antibodies, to be exempt from restrictive measures or deployed to jobs. It’s hard to imagine immunity being used to segregate people in America.
There may be ways to incorporate evidence of immunity into a person’s overall health that can be used to guide what precautions should be taken on the job and in personal lives. As states start to relax restrictions on economic and social activity, antibody test results can be helpful in assessing the risk of certain activities.
Health-assessment software such as CareEvolution’s “Safer Covid” tool can combine multiple health factors to evaluate a person’s total risk of contracting Covid or suffering a bad outcome. Such a “risk score” could at some point soon include antibody results and help inform decisions about behavior. How much information fed into these tools is up to the person using them. Americans can decide their own comfort level with offering personal health data. Similar tools already assess the risk of, say, stroke or diabetes.
There’s instinctual discomfort about using evidence of past immunity as a factor for decisions about health, work or even questions like whether it’s safe to visit someone in a nursing home. But there are ways to deploy immunity information to help us understand our own health status and keep us safer from Covid, without surrendering privacy.
Dr. Gottlieb is a resident fellow at the American Enterprise Institute and was commissioner of the Food and Drug Administration, 2017-19. He serves on the boards of Pfizer and Illumina and is a partner at the venture-capital firm New Enterprise Associates.
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