Pfizer's COVID-19 treatment Paxlovid has been hailed as a breakthrough in the fight against COVID-19. The pills have shown to dramatically reduce the risk of being hospitalized or dying for people who are at high-risk of COVID-19.
But mounting evidence suggests Paxlovid may not benefit everyone equally. The company recently announced the results of a new study that found the drug did not meaningfully benefit people without underlying medical conditions or no previous infection of COVID.
This comes weeks after the Biden administration announced plans to purchase 20 million treatment courses of the drug as it focuses on the Test-to-Treat initiative as part of the National COVID-19 Preparedness Plan.
Some infectious disease experts interviewed by ABC News said the new study could influence the way doctors prescribe the drug, potentially declining to prescribe it to vaccinated, otherwise healthy patients.
But overall, demand for the drug is likely to remain high because 60% of Americans are living with a chronic disease that qualifies them for the drug under its current authorization.
"Paxlovid is something that is targeted towards high-risk individuals, so the fact that it doesn't have a benefit to low-risk individuals isn't surprising to me," Dr. Amesh Adalja, an infectious disease specialist at the Johns Hopkins University Center for Health Security, told ABC News.
The Centers for Disease Control and Prevention has provided guidance that the drug is recommended for treatment of mild to moderate COVID-19 among people at high risk for severe disease.
"At this stage, the current recommendation under the EUA is for Paxlovid to be given to any high-risk patient who has symptomatic COVID, whether vaccinated or unvaccinated, as long as it is within five days of the onset of symptoms," Dr. Todd Ellerin, chief of medicine and director of infectious diseases at South Shore Health, told ABC News.
"If you're older, particularly over age 65, if you have underlying illnesses, if you're immunocompromised, those groups I think will continue to be targeted for Paxlovid," Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center, told ABC News.
While the CDC has published a list of medical conditions that would put someone at high risk for severe illness, some experts argue there may be ambiguity.
"High-risk isn't necessarily only objective criteria, like age, heart disease, etc. It's also a situation, like socioeconomic status and some of those disparities that exist. When you add all that up, I think that a large swath of people do qualify for Paxlovid potentially as high-risk," Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco, told ABC News.
Pfizer CEO Albert Bourla said the drug would continue to be an important treatment option.
"With up to 40-50% of people around the world estimated to be high risk, we believe there remains a significant unmet need for treatment options to help combat this disease, and we will continue to prioritize efforts to advance the development of Paxlovid," Bourla said in a press release.
Experts tried to compare that global context to the United States.
"When you look at the average body mass index (BMI) of men and women in the United States is 26, that puts you at a high-risk category and eligible for Paxlovid. So at least 50% of the country is eligible for Paxlovid that is infected with COVID," Ellerin said.
The CDC defines overweight people as those with a BMI of 25-30 and obese as those with a BMI over 30.
Doctors said there are serious considerations to weigh before prescribing Paxlovid. Drug-drug interactions may lead to serious or life-threatening drug toxicities, including medications such as cardiovascular agents and anticonvulsants. Meanwhile, Paxlovid carries a low risk of something called "COVID-19 rebound," where individuals experience a recurrence of symptoms or a new positive viral test after having tested negative, according to the CDC.
"When it comes to Paxlovid, at the individual level, there may not be so much downside, but we don't want to be inappropriately giving drugs to people where there would be no benefit and potentially some downside," said Dr. John Brownstein, Chief Innovation Officer at Boston Children's Hospital and an ABC News medical contributor.
A recent, small study estimated that less than 1% of patients experience a rebound of symptoms.
Brownstein remains optimistic that further research will clarify guidance on how best to prescribe the drug.
"I think there is a lot that needs to be understood, we have a lot of real-world data and so I think it is reasonable to understand how well it's working and because it is so widely available, this will not be a hard drug to study like many others. So, we should have a lot of evidence to support a very specific recommendation," Brownstein said.
Youri Benadjaoud is an MPH candidate at Brown University and a contributor to the ABC Medical Unit.