Should You Retest After Testing Positive for COVID-19?

A positive COVID-19 test can be jarring, but what to do after receiving one is clear: Isolate—specifically for five days, whether you're showing symptoms or not. The guidance for when you can (or whether you should) test yourself again after receiving a positive result, however, is a bit less straightforward.

Some people, either in hopes of cutting quarantine corners or out of curiosity for their condition, have taken to tracking their COVID status by testing daily with at-home antigen tests. But doctors warn against testing yourself for the virus every day—not necessarily because it's harmful, but because it's likely unhelpful.

Here, we dig into what the official guidance from the Centers for Disease Control and Prevention (CDC) says regarding when to retest after a positive COVID result, and what experts in the field most commonly suggest.

What the CDC says about retesting after a positive COVID test

The CDC recommends staying home or away from others for five full days if you test positive for COVID (with or without symptoms), or if you have symptoms, regardless of vaccination status. If you absolutely have to be around other people (say, if you share a home with others who are COVID-negative), you should wear a well-fitted mask.

After those five days, the CDC says you can end isolation if you didn't develop symptoms, or if you developed symptoms but have been fever-free for 24 hours (without the use of fever-reducing medicines) and your symptoms are improving. However, you still have to wear a mask for five more days, the CDC says.

For both of these scenarios, the CDC says retesting yourself is an option, not a requirement: "If an individual has access to a test and wants to test, the best approach is to use an antigen test towards the end of the five-day isolation period," the CDC guidelines read. "Collect the test sample only if you are fever-free for 24 hours without the use of fever-reducing medication and your other symptoms have improved." If you end up testing positive again, the CDC recommends you continue isolating until day 10.

This guidance differs a bit if you had severe illness from COVID-19, or if you have a weakened immune system: In that case, the CDC says you may require additional viral testing—molecular or antigen tests—to determine if and when it's safe to be around others. In that case, the best course of action is to talk with your doctor to determine a testing plan.

What experts say about retesting after a positive COVID test

If you found yourself feeling confused over the CDC guidelines for quarantine and isolation, you're not alone; the president of the American Medical Association (AMA), Gerald E. Harmon, MD, shared a statement on the matter on January 5. "A negative test should be required for ending isolation after one tests positive for COVID-19," Dr. Harmon wrote. "Reemerging without knowing one's status unnecessarily risks further transmission of the virus."

According to the AMA, an estimated 31% of people remain infectious after five days following a positive COVID test—and Dr. Heaton says this could result in "potentially hundreds of thousands of people" returning to work or school while they're still contagious.

That said, even an additional test after five days of isolation, may only be so helpful. "A negative antigen test at five days [after testing positive] tells you that the amount of virus present in your nose, saliva, or wherever you sampled from is low enough not to cause a positive test," Clare Rock MD, infectious disease physician, epidemiologist, and associate professor of medicine at Johns Hopkins School of Medicine, tells Health. That's because antigen tests, more so than PCR tests, are prone to false negatives. "It does not necessarily mean you are not still infectious to others, which is why it's very important to wear a mask," says Dr. Rock.

To make things even more confusing: Let's say you still get a positive COVID-19 test result, even after 10 days of isolation—that may not tell you everything you need to know, either. "Some people persist in getting a positive result many days after infection, when in theory they are considered noninfectious," Cheryl G. Healton, DrPH, dean of the School of Global Public Health at New York University, tells Health. Both antigen and PCR tests can detect dead virus fragments that may remain in the upper airway, even after you're no longer infectious, she says.

What should you do with this information?

Though the CDC guidelines are admittedly hard to interpret, they're the best course of action: If you've tested positive for COVID-19 (or if you have symptoms), isolate for at least five days or until you're fever free for 24 hours and your symptoms are improving, then continue to exercise caution by wearing a mask around others until 10 days have passed since your first positive test or symptom.

"The CDC guidance aligns with clinical experience that shows the bulk of people who are post-symptomatic five days after symptom onset are not actively infectious," says Dr. Healton. "The fact that tests can remain positive post-infection may be one reason why [the CDC] emphasized time [over testing to end isolation]."

If you would like to use an antigen test at the end of your five-day isolation period (and you have one available to you), you can go ahead and do that, but no more frequently than every three days after your initial five-day isolation, says Dr. Rock. Both Drs Rock and Healton say daily testing after a positive COVID test is not necessary. With more at-home tests available now—especially with the four free at-home tests each household in the US is able to order from the government—additional testing is more accessible for the general public.

At the end of the day, no test (or CDC guideline) is reliable enough to tell you with 100% accuracy whether you're still contagious, which is what retesting is really all about. "Being cleared for normal activities by your health care provider is the best course," Healton says. The same goes for wearing a mask out in public; the most protective ones—N95 respirators—help to best shield you and others from viral particles.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.

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