• People who take Pfizer's Covid antiviral treatment Paxlovid shortly after infection may reduce their risk of developing long Covid, regardless of their age, vaccination status or infection history, a new study shows.
• The study, published in JAMA Internal Medicine, found that people who took Paxlovid within five days of a positive Covid test saw a 26% lower risk of long Covid compared with those who didn't.
• The findings suggest the benefits of Paxlovid may go beyond what the drug is designed for, which is to treat adults and children at high risk of getting severely sick from Covid.

People who take Pfizer's Covid antiviral treatment Paxlovid shortly after infection may reduce their risk of developing long Covid, regardless of their age, vaccination status or infection history, new research suggests.

The study, published in the journal JAMA Internal Medicine on Thursday, found that people who took Paxlovid within five days of a positive Covid test saw a 26% lower risk of long Covid compared with those who didn't receive it. More than 35,000 people took the oral Covid pill in the study, while 246,000 did not. 

The study only enrolled people who are eligible for Paxlovid under emergency use authorization. That includes adults over 50, or those who have an underlying medical condition such as high blood pressure or diabetes.

The findings suggest the benefits of Paxlovid may go beyond what the drug is designed for, which is to treat adults and children who are at a higher risk of ending up in the hospital or dying from a Covid infection. The drug still demonstrated that intended benefit in the study, lowering the risk of death by 47% and hospitalization by 24% about a month after initial infection.

The new study comes as researchers work to fill the knowledge gap about long Covid, an often debilitating condition with limited data and no proven treatment available.

Long Covid refers to new, returning or ongoing health issues more than four weeks after an initial Covid infection, according to the Centers for Disease Control and Prevention. Those issues can include fatigue, difficulty breathing, chest pain and brain fog, and can last for weeks, months or even years. The CDC estimates that 1 in 5 Covid survivors ages 18 to 64, and 1 in 4 survivors 65 or older, have an ongoing health issue that might be attributable to a previous infection. 

Most of what is known about long Covid is that certain people are more at risk of it, and Covid vaccination likely provides some protection against it, according to Dr. Jessica Bender, co-medical director at the University of Washington's post-COVID-19 Rehabilitation and Recovery Clinic. She called the new study "very exciting and promising" because it's the first to show an association between Paxlovid and a decreased risk of long Covid.

Dr. Anita Chopra, a board-certified internal medicine physician who sees patients at a University of Washington Medicine Primary Care center, added that prescribers can use the study results to encourage the uptake of Paxlovid. Eligible patients will be more reassured knowing the drug may lead to a significant reduction in their chances of developing the post-Covid condition, she said.

But Chopra acknowledged that the study was observational, meaning the researchers observed participants who did or didn't take Paxlovid without intervening. It wasn't a randomized controlled study – considered the gold standard for clinical research – where researchers intervene and can better examine a potential cause-and-effect relationship between receiving a drug like Paxlovid and an outcome. 

Bender emphasized the need to conduct a randomized controlled study to "replicate these findings." 

She said the study's other limitation is it identified participants using health-care databases of the Department of Veterans Affairs. The researchers need to conduct studies in other patient populations outside of that health-care system, according to Bender.

The study comes as Paxlovid inches closer to winning full approval from the Food and Drug Administration, with the agency's advisors voting overwhelmingly in support of the drug last week. The FDA is expected to make a decision in May. 

More than 12 million courses of Paxlovid have been delivered to pharmacies across the U.S., according to the latest federal data. Roughly 8 million Americans have taken the drug, with about 1.3 million doses available nationwide.

Correction: Bender said the study's other limitation is it identified participants using health-care databases of the Department of Veterans Affairs. An earlier version misstated the name of the department and the doctor's surname.