Reports of ‘Paxlovid rebound’ increase, Covid researchers scramble for answers

As reports of ‘Paxlovid rebound’ increase, Covid researchers scramble for answers Early on, clinicians ruled out the most concerning possibility for Paxlovid rebound: that the virus was evolving resistance to the drug, a prospect that could undermine the treatment before it even had time to take off. Jason Mast STAT

As he was treating some of the nation’s first coronavirus patients, Andre Kalil noticed something unusual about the new virus: Patients didn’t always progress linearly. They’d get better, then worse. Then sometimes better again.

Initially, most researchers figured these undulating symptoms were collateral damage, as a riled-up immune system kept firing long after most of the virus was gone. Sometimes, though, Kalil could swab the lungs of a patient in the ICU and find virus still replicating weeks after they were admitted. Often, the amount of virus bounced up and down by the day.

“I cannot tell you how many times I’ve seen patients that late in the disease, with very, very high viral load,” said Kalil, a physician and professor at the University of Nebraska Medical Center, home to the nation’s only federal quarantine center. “This virus is different than other viruses in the past. It has the capacity to replicate for much longer.”

Kalil has been thinking about those early patients again as researchers around the world race to solve a growing mystery: Paxlovid rebound.

Almost 90% effective at preventing hospitalizations from Covid-19, Pfizer’s antiviral pill has quickly become one of the most powerful additions to the pandemic arsenal since the advent of mRNA vaccines. But as it’s become more widely available, a growing number of people have found the drug only temporarily effective.

...

These stories raise important questions about how doctors should use the most effective Covid-19 treatment to date: It might mean some patients need longer courses of medicine; guidelines for who should take it could be refined; recommendations for exiting quarantine may have to be updated. ...

ALSO SEE: The terrible taste side effect of Paxlovid