Boston Doctors Seeing More Paxlovid Rebound in COVID Patients

Some people who take Paxlovid, an antiviral for COVID-19, see their symptoms rebound after briefly recovering, prompting concerns about taking the drug at all.

The Centers for Disease Control and Prevention issued in an advisory about the phenomenon last month. Since then, doctors and infectious disease experts in Boston have been flooded with questions from their patients about the drug, which was approved for people who have mild or moderate COVID but are at high risk of a severe case.

Tufts Medical Center's Dr. Shira Doron, Boston Medical Center's Dr. Sabrina Assoumou and Brigham and Women's Hospital's Dr. Daniel Kuritzkes shared what they've seen and what they tell their patients about whether or not to take Paxlovid during NBC10 Boston's latest "COVID Q&A" discussion.

What is Paxlovid rebound?

Two to eight days after taking the drug regimen and testing negative, some patients test positive again and see their symptoms reappear.

"It's this phenomenon that really started anecdotally with people reporting that they took Paxlovid -- they felt better, often immediately," Doron said. "People were repeatedly testing themselves at home, seeing that, along with the resolution of their symptoms, they would have a test that turned negative and then symptoms return and the test becomes positive again."

"We hadn't really heard about that from the clinical trial," Doron noted.

While Pfizer’s clinical trial identified similar rates of COVID rebounds among participants who had recently finished Paxlovid and those who recently got a placebo at around 2%, local experts said it appears to be happening more frequently.

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"Anecdotally, it seems like it's happening more frequently than what what was reported to clinical trials," Assoumou said. "We're actually investigating that and trying to get more and more information."

Doron questioned whether the Paxlovid rebound is occurring more frequently due to a difference between delta, which was the predominant variant of coronavirus during the trial, and omicron, the only strain that's circulating now.

"The question becomes, is this rebound symptomatology and positive test a natural phenomenon of COVID-19 that we just really didn't recognize? That would happen in anybody? Or is it actually being driven by Paxlovid," Doron posed. "It may not be Paxlovid rebound, it may be COVID rebound, but we sure hear about it a lot."

Should I take Paxlovid?

Experts said that rebounds don't necessarily mean Paxlovid doesn't work. 

"The message I want to convey is that, if you do qualify and if you're at risk, I think that this is a phenomenal drug that could really make a difference in keeping people outside of the hospital and not needing to be hospitalized," Assoumou said. "So I would say talk to your clinicians and talk to your healthcare professional to make sure that you get the best advice."

Pfizer's clinical trial showed that Paxlovid lowered the risk of hospitalization or death among high-risk COVID patients by 88% within five days of symptoms. The National Institutes of Health still recommends it over other treatments for mild or moderate COVID.

"Anecdotally, it seems like it's happening more frequently than what was reported to clinical trials."

Boston Medical Center's Dr. Sabrina Assoumou

"Unless there were evidence that taking Paxlovid increased the risk of rebound and therefore led to higher length of needing to quarantine, which I don't think exists currently, there's no good reason for people to avoid taking Paxlovid if they fall into the risk categories of people who would benefit," Kuritzkes said.

But some people have been reluctant to take the drug since the CDC recommended that people with COVID rebounds start their isolation over again. Weighing the risk of infection versus Paxlovid rebound is a "really, really difficult question to answer," Doron said.

"For many people that really changes the risk-benefit, because for many people, it's the isolation that's one of the worst parts of having COVID," Doron said. "I just tell it like it is. And I don't know for sure right now. I say, 'I don't know what the frequency of Paxlovid rebound is,' and we talk it out."