Rare Cases of COVID Relapse Seen With Pfizer Pill

TUESDAY, May 10, 2022 (HealthDay News) -- Rare cases of COVID patients relapsing after taking the antiviral pill Paxlovid are raising questions among some experts.

An earlier study of 1,000 adults showed that Paxlovid was highly effective at preventing severe COVID and the U.S. government has bought enough of the drug to treat 20 million people.

But there have been reports of symptoms returning in patients several days after completing the five-day regimen of Paxlovid, prompting some doctors to wonder if these patients are still contagious and should take a second round of the drug.

But the U.S. Food and Drug Administration last week advised against a second round, saying there is little risk of severe illness or hospitalization among patients who relapse after taking Paxlovid.

The Pfizer drug was tested and authorized based on its effectiveness against the Delta variant and may be less effective against Omicron, noted Dr. Michael Charness, who works for Boston's VA health system.

He treated a 71-year-old vaccinated patient whose symptoms eased but then returned, along with a surge in virus levels, nine days into his bout of COVID-19.

“The ability to clear the virus after it's suppressed may be different from Omicron to Delta, especially for vaccinated people,” Charness told the Associated Press.

In the original study, virus levels rose after 10 days in 1% to 2% in those taking either the drug or dummy pills, Pfizer and the FDA have noted, the AP reported. That rate was about the same among people taking the drug or dummy pills, “so it is unclear at this point that this is related to drug treatment,” the FDA stated, the AP said.

Another possible explanation for rare cases of relapse among patients taking Paxlovid is that the dose isn't strong enough to fully suppress the virus in all people, said Andy Pekosz, a virologist at Johns Hopkins University in Baltimore. That could lead to coronavirus mutations that are resistant to the medication, he said.

“We should really make sure we’re dosing Paxlovid appropriately because I would hate to lose it right now,” Pekosz told the AP. “This is one of the essential tools we have to help us turn the corner on the pandemic.”

More information

Visit the Yale School of Medicine for more on Paxlovid.