Comment: Lack of studies leaves us flying blind with Paxlovid

The covid treatment is effective for older patients, but data is thin on whether it’s helping others.

By Lisa Jarvis / Bloomberg Opinion

In the month since I last wrote about the dearth of data on Paxlovid’s benefit for vaccinated and younger covid-19 patients, infections have soared and prescriptions of the antiviral have skyrocketed. As of June 1, more than 1 million courses of the drug have been administered in the U.S.

Roughly one-third of these pill packs have been prescribed just since May 17. At this point, nearly half of all covid patients are taking antivirals, mostly Pfizer’s Paxlovid, Evercore ISI analyst Umer Raffat estimates.

Yet studies to understand which patients benefit from the treatment and which ones do not are slow in coming. Regulators are left to rely on other countries for data on how well this drug works in the real world.

The U.S. Food and Drug Administration authorized Paxlovid for anyone ages 12 and up with a recent covid diagnosis and a risk factor for severe disease. Those factors, which include conditions such as diabetes and obesity, encompass a broad swath of the population.

A new study from Israel suggests that very few of those patients actually benefit from Paxlovid.

The Israeli researchers wanted to understand whether the drug was effective specifically against omicron in people 40 or older and at high risk of serious disease. Their study has yet to be peer reviewed, and it has a couple of limitations: It’s an observational study — a look back at records from a large health-care system — rather than a placebo-controlled clinical trial. And the results gathered on younger, vaccinated patients are less conclusive than the signal found in older ones.

Even factoring in these limitations, however, the findings call into question the free flow of Paxlovid in the U.S.

The drug very clearly helps keep older, unvaccinated or under-vaccinated people who have been infected with covid out of the hospital. For people 65 or older, Paxlovid lowered the risk of hospitalization by 67 percent and of death by 81 percent. This real-world evidence confirms what Pfizer saw in the clinical trials it ran before omicron swept through.

But people between the ages of 40 and 65 seemed not to benefit from the drug. And even those in the older group who had been previously exposed to the virus through vaccination, previous infection or both saw a relatively small benefit from Paxlovid.

Still in need of study is the question of why some people who take Paxlovid get better, only to see their illness rebound. These cases seem to occur in only a small percentage of patients, but given current prescription rates, that adds up to thousands of people.

On Wednesday, Albert Bourla, Pfizer’s chief executive officer, said these rebounds don’t seem to be caused by the virus becoming resistant to the drug. Bourla seemed confident that resistance would not be an issue in the near term, because Paxlovid is given in a dose that quickly suppresses viral load, and it targets a protein that is slow to change.

Pfizer is now planning a trial to investigate whether giving a second course of Paxlovid is effective in rebound cases. The National Institutes of Health, too, plans to study the rebound issue. But so far neither organization has said when those trials might start.

Paxlovid has been a powerful addition to the covid arsenal, protecting older, especially unvaccinated people from being hospitalized or dying. And there’s a chance this drug helps enough people feel better and get back to work faster, or reduces their risk of long covid, to merit wider use.

But U.S. health authorities are missing out on a critical chance to study the drug’s effectiveness in greater detail; to better understand who it can’t help and refine official guidance on which patients should be given prescriptions.

Lisa Jarvis is a Bloomberg Opinion columnist covering biotech, health care and the pharmaceutical industry.

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