As more doctors prescribe Pfizer’s powerful COVID-19 pill, new questions are emerging about its performance, including why a small number of patients relapse after taking the drug.
Paxlovid has become a well-known choice against COVID-19 due to its home comfort and impressive results in curing serious illness. The US government has spent more than $10 billion to buy enough pills to treat 20 million people.
But experts say much still remains to be learned about the drug, which was approved in December for adults at high risk of severe COVID-19, based on a study in which 1,000 The adults had received the drug.
Why do some patients reappear?
Doctors have started reporting rare cases of patients whose symptoms return several days after completing a five-day regimen of Paxlovid pills. This has prompted questions about whether those patients are still contagious and should receive a second course of paxlovid.
Last week, the Food and Drug Administration weighed in. It advised against a second round because there is little risk in patients with severe illness or hospitalization.
Dr. Michael Charnes reported last month about a 71-year-old vaccinated patient who noticed that his symptoms subsided but then returned, with the virus level rising nine days after his illness.
Charnes says that Paxlovid is a highly effective drug, but he wonders if it might be less potent than the current Omron version. The $500 drug treatment was tested and approved based on its performance against the delta version of the coronavirus.
“The ability to suppress the virus after it clears it may differ from Omicron to Delta, especially for people who are vaccinated,” said Charnes, who works for Boston’s VA Health System.
Can some people simply be susceptible to a relapse? Both the FDA and Pfizer state that 1% to 2% of people in Pfizer’s original study saw their virus levels relapse after 10 days. The rates were roughly the same in people taking the drug or counterfeit pills, “so it’s unclear at this point whether this drug is related to treatment,” the FDA said.
Some experts point to another possibility: The Paxlovid dosage is not strong enough to completely suppress the virus. Andy Pecoz of Johns Hopkins University worries that the drug may promote a resistant mutation.
“We should really make sure we’re dosing Paxovid appropriately because I’d love to lose it now,” said Pecos, a virologist. “It’s one of those essential tools to help us turn the corner on the pandemic.”
How well does Paxlovid work in people who have been vaccinated?
Pfizer tested paxlovid in the highest-risk patients: unvaccinated adults with no prior COVID-19 infection and other health problems, such as heart disease and diabetes. The drug reduced his risk of hospitalization and death from 7% to 1%.
But that doesn’t reflect the vast majority of Americans today, where 89% of adults have received at least one shot. And about 60% of Americans have been infected with the virus at some point.
“That’s the population I care about in 2022 because that’s what we’re looking at – vaccinating people with COVID – so do they benefit?” asked University of Minnesota researcher and physician Dr. David Boulware.
There is no clear answer yet for vaccinated Americans, who already have hospitalization rates of less than 1%.
This may come from a large ongoing Pfizer study involving people at high risk of vaccination. No results have been published; The study is expected to end in the fall.
Pfizer said last year that early results showed that Paxlovid had failed to meet the study’s goals of resolving symptoms and reducing hospitalizations. It recently stopped enrolling anyone who had received vaccinations or boosters in the past year, a change Boulware says is not benefiting those patients.
At a minimum, the initial data should be released to federal officials, Boulware said. “If the US government is spending billions of dollars on this drug, what is the obligation to release that data so they can formulate a good policy?”
Can Paxlovid be used to help prevent COVID-19 infection?
Pfizer recently reported that giving Paxlovid to family members of people infected with COVID-19 did not significantly reduce their chances of catching it. But this is not the end of the story. Pfizer is studying several other potential benefits of early use, including whether PaxLovid reduces the length and severity of COVID-19 in homes.
“It’s a high bar for protecting against infection, but I’d love to see data on how PaxLovid fared against severe disease because it could be more effective there,” Pecoz said.