Editor’s Note: Every Wednesday, James Hamblin takes questions from readers about health-related curiosities, concerns, and obsessions. Have one? Email him at email@example.com.
Dear Dr. Hamblin,
I’m a senior who has spent considerable effort at staying out of harm’s way. My wife and I spent much of March through June at home, making quick shopping trips when needed. We are always masked when indoors in a public space, but we do get within six feet of others when grocery shopping or eating outdoors with a few friends. Surely we have been exposed, at least slightly, to low quantities of the coronavirus over the course of the pandemic. Even if we don’t get sick, is our immune system activated? Can we develop antibodies through repeated low-dose exposures?
That’s the dream scenario: building up immunity without getting sick. The short answer is that it’s possible. The long answer is that it’s not very likely. At least not yet.
Many people have tested positive for antibodies, to their surprise, without having had symptoms or known contact with an infected person. It seems clear that you don’t even need repeated low-dose exposures to the coronavirus to develop antibodies. A single exposure could do it. Unfortunately, immunity is rarely so simple. The dream scenario probably does occur occasionally. But although many people have tested positive for antibodies without getting sick (or, at least, without getting seriously sick), that doesn’t mean they’re immune.
The main issue is that not all coronavirus antibodies are the same. Some antibodies latch onto the virus, but won’t stop its spread. Detecting these types in someone’s blood can tell you that that person has been exposed to the virus, but not that they’re immune. Other antibodies, known as neutralizing antibodies, go right for the virus’s Achilles’ heel. They bind to the spike proteins on its surface, the grappling hooks that it uses to latch onto human cells. By taking out those spikes, they render the virus incapable of spreading within the body and causing disease. Only some people who test positive for antibodies have neutralizing antibodies. Most current antibody tests can’t tell the difference. Only last week did the U.S. Food and Drug Administration give emergency-use authorization for the first test that singles out neutralizing antibodies.
Neutralizing antibodies seem to be less common after an asymptomatic infection than after a serious case of COVID-19. Whatever antibodies do develop in those cases seem to fade more quickly, too. So a brief exposure to a tiny amount of virus in a grocery store may be enough to turn your antibody test positive, but it seems less likely to confer meaningful, lasting protection than if you’d had a serious case of COVID-19. The degree to which the severity of COVID-19 is related to the types of antibodies that develop remains unclear, and we can expect outliers of all sorts to be reported. But don’t mistake a single report of a person who had tons of protective antibodies without ever getting sick for the norm. For now, no one should behave any differently right now just because they’ve had a positive antibody test. We still need to get better at deciphering which antibodies people have—and how many are needed to confer immunity—before we can assure them that they are protected.
All of these variables are why vaccination is so complex, and usually takes many years to get right. The goal is to create that dream scenario you described: to stimulate people’s immune system into developing neutralizing antibodies that last, and to do so without causing side effects. Threading that needle is always a challenge, but especially with a virus like this one, which affects people in such different ways. That’s why this month’s news of the apparent effectiveness of the Pfizer and Moderna vaccines—90 percent and 95 percent, respectively according to preliminary data—was so surprising. Even more amazing will be if the number stays that high over time, and no significant side effects are reported. But it looks like, once clinical trials are complete, we should have a vaccine that can reliably deliver that dream scenario: a protective immune response without ever getting sick, or even infected.
The bottom line is that your question is an interesting academic one, but the answer shouldn’t change anyone’s day-to-day life. In reality, most infected people have at least some symptoms, and many get extremely sick. More than 1,000 Americans are dying each day. Many others are developing chronic disease. There’s no reason to assume that low-level exposure to the virus is beneficial. Flirting with mild exposure is not something to even consider doing deliberately. Even if you didn’t get sick, you could become an asymptomatic carrier and spread the virus, infecting and potentially killing other people. And you’d probably have no immunity to show for it.
“Paging Dr. Hamblin” is for informational purposes only, does not constitute medical advice, and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. By submitting a letter, you are agreeing to let The Atlantic use it—in part or in full—and we may edit it for length and/or clarity.