THURSDAY, March 6, 2025 (HealthDay News) --  The antiviral drug Paxlovid may not offer much protection against COVID-related hospitalizations or deaths for vaccinated older adults after all.

Research published recently in JAMA Network Open looked at data from more than 1.6 million adults ages 65 to 74 in Ontario, Canada, during 2022.

Most participants (nearly 88%) had received at least two doses of the COVID vaccine, and only certain high-risk groups or adults 70 and older were eligible for Paxlovid at the time.

The study found that Paxlovid did not significantly reduce the risk of hospitalization or death from COVID in this mostly vaccinated population.

“We were surprised and disappointed,” lead study author John Mafi, an associate professor of medicine at the David Geffen School of Medicine at UCLA, told The Washington Post. 

“We concluded that it’s because it’s a highly vaccinated group with 88 percent fully vaccinated,” he added.

The findings could help older adults weigh the benefits and costs of taking Paxlovid.

“The cost is part of the calculus because it’s $1,650 per treatment course,” Mafi said. “I think that needs to be part of the conversation.”

A spokesperson for Pfizer, which makes Paxlovid, said the company stands by its effectiveness for patients at high risk for severe illness.

What's more, Paxlovid may still be helpful for certain high-risk groups, Mafi said.

“If you’re immunosuppressed, if you have cancer, chemotherapy, if you are frail, if you’re living in a nursing home, if you have end-stage kidney disease, if you’re an organ transplant recipient, those are very high-risk conditions,” he told The Post. “I would be more cautious in those groups.”

Paxlovid, a combination of nirmatrelvir and ritonavir, has been shown to reduce hospitalizations and deaths in unvaccinated, high-risk adults. 

But prior research found it didn’t significantly shorten COVID symptoms in vaccinated adults.

At best, the drug lowered hospitalization risk by 1.3 percentage points in this new study.

“If you are vaccinated without additional risk factors, I wouldn’t prescribe Paxlovid, and I probably wouldn’t take it if I was a patient,” study co-author Dr. Peter Wu, associate professor of medicine at the University of Toronto, told The Post.

More information

Yale Medicine has more about Paxlovid.

SOURCE: The Washington Post, March 5, 2025