How Common Is Paxlovid Rebound?

After taking the antiviral pill Paxlovid for COVID-19, some people report testing positive for the virus again. This so-called "Paxlovid rebound" is rare, but can affect anyone—including President Biden.

According to his social media, the President tested positive for COVID-19 on July 21. He quarantined until July 27, when he tweeted a picture of a negative rapid test.

“Back to the Oval,” Biden wrote on Twitter. “Thanks to Doc for the good care, and to all of you for your support.” In a later tweet, Biden expressed his gratitude for Paxlovid.

But three days later, on July 30, the President revealed that he had tested positive for COVID-19 again.

“Folks, today I tested positive for COVID again,” read Saturday's tweet. “This happens with a small minority of folks. I’ve got no symptoms but I am going to isolate for the safety of everyone around me. I’m still at work, and will be back on the road soon.”

How common is a COVID rebound after Paxlovid, really? And what should you do if it happens to you?

What Are the Odds of a COVID Rebound?

According to research, testing positive soon after COVID-19 recovery with Paxlovid is fairly rare.

A June preprint study shows 3.53% of people may experience a rebound within 7 days of taking Paxlovid, but the rate of symptomatic rebound is only 2.31%.

After 30 days, the chance of a COVID rebound after Paxlovid increases slightly to 5.4%.

Some researchers suspect more people may be rebounding after Paxlovid than we think. Michael Mina, MD, PhD, chief science officer at eMed, tweeted on Monday that rebounds are happening, and stressed the importance of post-quarantine testing to reduce the spread of COVID.

Mina emphasized, however, that Paxlovid is crucial to keeping vulnerable COVID patients out of the hospital.

A Rebound Is Not a Relapse

Getting a positive test after testing negative, like Biden did, is different than experiencing a symptomatic COVID-19 relapse.

“When we think about a relapse, we think about clinical symptoms: Someone has a repeat onset of fever or sore throat or congestion,” Jeffrey Klausner, MD, MPH, an infectious disease specialist and clinical professor of Population and Public Health Sciences at the University of Southern California, told Verywell.

In contrast, Biden experienced a “reversal” in his body's clearance of the virus. His physician notes his only symptom is a loose cough. Klausner says this appears to be less dangerous.

When Should You Re-Test?

Laolu Fayanju, MD, a family medicine specialist at Oak Street Health, which treats many Medicare patients and seniors, told Verywell that it can be a good idea to test again for COVID-19 if you experience a return of symptoms after seemingly recovering. 

“If you've been really paying attention to your body and you don't feel well, test yourself again,” Fayanju said. “See if the virus has returned.”

Biden’s post-Paxlovid case was asymptomatic, however, so he didn’t catch it by tuning into bodily queues. He caught it with regular testing.

If you are asymptomatic, Fayanju suggests re-testing two to three days after your initial negative test. But it's not a hard and fast recommendation.

“We don't yet have any clear guidance, or any guidelines, on how frequently to re-test, which puts us in a tough situation as clinicians on how to advise our patients,” Fayanju said.

Can You Take Paxlovid a Second Time?

Whether or not you can take Paxlovid again after a Paxlovid rebound depends on whether or not you're symptomatic.

According to Klausner, the antiviral is most effective at alleviating symptoms and keeping people out of the hospital. Without symptoms, there is no need for this type of treatment.

Fayanju doesn’t recommend a repeat Paxlovid protocol for asymptomatic people who start to test positive again, either. But he might recommend it for someone who rebounds with symptoms if those symptoms are severe.

However, in his experience, this hasn't happened. Among all the patients for whom Fayanju has prescribed Paxlovid, he is unaware of any rebounds.

Optimizing Antiviral Therapies

More studies on Paxlovid may help providers optimize its performance.

Right now, the Food and Drug Administration (FDA) has only authorized a five-day course of Paxlovid. The dosage consists of three tablets taken together orally twice a day—so 30 pills overall.

Klausner says he's been experimenting with the number of days he prescribes the drug for, as well as the dosage.

For 40 of his patients, he prescribed the drug for eight-day use. He instructed them to take two pills a day for the first two days, and one pill a day for the following six days.

“In my experience—which is limited to those 40 patients—extending the duration of treatment to eight days has reduced this frequency of test reversal,” Klausner said.

Fayanju, who prescribed Paxlovid for the authorized five-day use, said he worries that stretching out the regimen could dilute the drug’s effectiveness.

“There's going to be a lot of trial and error that providers and clinicians will attempt as they figure out how to best use this medication,” Fayanju said. "COVID humbles us all, both in what we don't know about it and the sheer extent of what it does to our patients."

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.