Over the past few days, several people close to Vice President Mike Pence have tested positive for COVID-19. Because Pence received a negative COVID-19 test, the White House argued that he’s safe to go on campaigning. And it’s understandable that you (and Pence) would want to rely on a negative COVID-19 test to reassure yourself that you aren’t going to infect others. But that’s not really how it works—and a single negative test result isn’t a guarantee that you don’t have the virus.
There are a few different types of COVID-19 tests out there now. The gold standard of coronavirus tests is still the nasal swabs, which use the polymerase chain reaction (PCR) to look for the presence of viral RNA in your sample. These tend to be the most accurate, but are also invasive and, depending on how many other people are also getting tested in your area, it may take a while for your results to come back with these tests. Other types of tests, rapid COVID-19 tests, tend to be cheaper and faster, but are often slightly less accurate in their results.
There are also coronavirus antibody tests that purport to tell you if you have antibodies to the virus after an infection, but it’s not entirely clear what the results from those tests really mean. And having a positive result (meaning you have antibodies to the virus) definitely should not be taken as a sign that you’re now “immune” to the virus.
Coronavirus tests are especially helpful when used to diagnose the infection in people who have symptoms of the virus and those who’ve been exposed to someone with a known case of COVID-19, whether or not they have symptoms. Experts also believe that frequent and widespread rapid testing can help catch an outbreak in its early stages at places like college campuses, where there are a lot of people in close proximity.
But the tests we have aren’t perfect. For instance, we know that the tests are more likely to give you a false-negative results (meaning you have COVID-19 but the test gives you a negative result) the earlier on in your illness. It takes an average of five days after exposure to COVID-19 for symptoms to show up (though it can take as long as 14), and a recent study in the Annals of Internal Medicine suggests that the PCR tests are least accurate in those first four days before you have symptoms. The rate of false-negatives on day four was 67%, it was 38% on day five, and dropped to 20% on day eight in this study.
“If you test negative for COVID, it doesn’t mean you don’t have COVID. It only means you don’t have enough virus to detect,” Rachel Roper, Ph.D., associate professor of microbiology and immunology at East Carolina University, explained on Twitter. “You could be in the incubation phase. Every person who ever got COVID would have tested negative one day and positive the next.”
That’s why experts told SELF previously that it’s best to wait—and preemptively quarantine yourself—for at least a few days after a possible exposure to the coronavirus before getting tested. Even if you get a negative test once, you may need to get tested again in a few days if you start to develop symptoms or to confirm the negative result. But even after a negative test, if you’re a close contact of someone with a confirmed case of COVID-19, the Centers for Disease Control and Prevention (CDC) recommend that you still quarantine for a full 14 days after the exposure.
For all of these reasons, you shouldn’t see a negative test result on its own as a sign that you’re free and clear to interact with people in high-risk situations, like indoor mask-less gatherings with your friends, especially if you’ve had exposure to someone with a confirmed case of COVID-19. In fact, relying solely on testing “can do more harm than good because they provide a false sense of comfort and let people drop their guard,” Ali Nouri, Ph.D., molecular biologist and president of the Federation of American Scientists, said on Twitter.
The safest way to hang out with your friends, family, or anyone else you don’t currently live with is still to do so virtually. If you want to see people in person, it’s crucial to lower the risks as much as possible by wearing masks, ensuring people stay socially distanced, holding the event outside or in a space with adequate ventilation, encouraging those who aren’t feeling well to stay home, and limiting the number of people there, according to the CDC. Requiring everyone to have a negative COVID-19 test before they arrive might give you an extra sense of safety, but isn’t a substitute for those other essential precautions.
Coronavirus tests are a crucial piece of our fight against COVID-19, and we should be doing a lot more of it. But these tests are most effective at preventing the spread of COVID-19 when used alongside our other public health practices, including social distancing, wearing masks, avoiding crowds, and washing our hands frequently. Testing is one part of that plan—not a substitute for it.