Pfizer Covid pill showed no benefit in younger adults - study

Doses of the anti-viral drug Paxlovid have been found to be less effective on younger people. Photo / AP

Pfizer's Covid-19 pill appears to provide little or no benefit for younger adults, while still reducing the risk of hospitalisation and death for high-risk seniors, according to a study published this week.

The results from a 109,000-patient Israeli study are likely to renew questions about the US government's use of Paxlovid, which has become the go-to treatment for Covid-19 due to its at-home convenience. The Biden administration has spent more than $10 billion purchasing the drug and making it available at thousands of pharmacies through its test-and-treat initiative.

The researchers found that Paxlovid reduced hospitalisations among people 65 and older by roughly 75 per cent when given shortly after infection. That's consistent with earlier results used to authorise the drug in the US and other nations.

But people between the ages of 40 and 65 saw no measurable benefit, according to the analysis of medical records.

The study has limitations due to its design, which compiled data from a large Israeli health system rather than enrolling patients in a randomised study with a control group - the gold standard for medical research.

The findings reflect the changing nature of the pandemic, in which the vast majority of people already have some protection against the virus due to vaccination or prior infection. For younger adults, in particular, that greatly reduces their risks of severe Covid-19 complications. The Centers for Disease Control and Prevention recently estimated that 95 per cent of Americans 16 and older have acquired some level of immunity against the virus.

"Paxlovid will remain important for people at the highest risk of severe Covid-19, such as seniors and those with compromised immune systems," said Dr David Boulware, a University of Minnesota researcher and physician, who was not involved in the study. "But for the vast majority of Americans who are now eligible, this really doesn't have a lot of benefit."

A spokesman for Pfizer declined to comment on the results, which were published in the New England Journal of Medicine.

The US Food and Drug Administration authorised Paxlovid late last year for adults and children 12 and older who are considered high risk due to conditions like obesity, diabetes and heart disease. More than 42 per cent of US adults are considered obese, representing 138 million Americans, according to the CDC.

At the time of the FDA decision, there were no options for treating Covid-19 at home, and Paxlovid was considered critical to curbing hospitalizations and deaths during the pandemic's second winter surge. The drug's results were also far stronger than a competing pill from Merck.

The FDA made its decision based on a Pfizer study on high-risk patients who hadn't been vaccinated or treated for prior Covid-19 infection.

"Those people do exist but they're relatively rare because most people now have either gotten vaccinated or they've gotten infected," Boulware said.

Pfizer reported earlier this summer that a separate study of Paxlovid in healthy adults - vaccinated and unvaccinated - failed to show a significant benefit. Those results have not yet been published in a medical journal.

More than 3.9 million prescriptions for Paxlovid have been filled since the drug was authorised, according to federal records. A treatment course is three pills twice a day for five days.