Paxlovid, the only drug people can take at home to treat an active case of Covid, is now being studied as a potential treatment for those who have remained ill months or even years after infection.
“There are people who are still suffering,” said Dr. Linda Geng, co-director of the Stanford Post-Acute Syndrome Clinic in California. “We need to find effective therapies.”
There are no proven treatments for prolonged Covid.
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Geng and his colleagues at Stanford Medicine have embarked on the first clinical trial to test whether Pfizer’s Paxlovid can help alleviate symptoms of constant fatigue, weakness or brain fog. The antiviral has already been shown to be effective in protecting against serious illness if used within five days of illness. It prevents the virus from reproducing inside the body.
Could that same mechanism work long after the onset of symptoms?
No one knows exactly what causes the variety of persistent problems associated with prolonged covid. One of the leading theories is that the body may harbor troublesome bits of leftover virus.
“There are clues that are piling up,” Geng said, pointing to research that detected the virus in the intestine, as well as in stool Y blood samples months after initial infection.
“It is known that covid can go to multiple sites in the body,” he said. “The question is, does it settle there? And is it quiet enough that our immune systems don’t get rid of it properly?”
The researchers hypothesize that Paxlovid may have a measurable impact on that leftover virus, if that is what causes long covid.
stanford study aims to enroll 200 adults who have had prolonged symptoms of Covid for at least three months, without a recent diagnosis of the disease.
Half of them will receive the real drug, while the rest will receive a placebo. While Paxlovid is usually given for five days, this study will have participants take it for 15. This is, in part, to address the possibility that the drug may need longer to work well. Many newly diagnosed Covid patients have reported rebound symptoms after their typical five-day course of treatment.
Results are expected sometime next year.
There is already evidence that people taking Paxlovid for covid are less likely to develop lasting symptoms. A Department of Veterans Affairs to study published earlier this month found that people who received the antiviral right after their covid diagnosis were 26% less likely than patients who did not take the drug to have ongoing symptoms three months later.
The findings of the VA study may not apply to everyone. All the participants were at least 60 years old or had other health problems that would increase the risk of complications.
Dr. Ziyad Al-Aly, a clinical epidemiologist at Washington University in St. Louis, led the study. The lead long-Covid researcher said that while he is eager to see how Paxlovid fares in the Stanford study, he suspects the drug may not be helpful after someone has already been suffering for a while.
“We really feel that with long covid, you shouldn’t wait until you already have all these issues to address them. We think it is too late,” she said. “You want to nip it in the bud.”
Al-Aly’s team also plans to study Merck’s Covid antiviral, molnupiravir. That drug is licensed for use in the early days of an infection, but only in patients who for whatever reason cannot take Paxlovid.
The American Academy of Physical Medicine and Rehabilitation estimates that 29 million Americans have a lot of Covid.
Some recover after weeks or a few months.
Others get worse, especially if they are reinfected, said Dr. Monica Verduzco-Gutierrez, chair of the department of rehabilitation medicine at UT Health San Antonio Long School of Medicine. She is not involved in either the Stanford or the VA investigation.
“If they get sick with Covid again, they can start from scratch or even get worse,” he said.
Verduzco-Gutiérrez said that studying Paxlovid in people with prolonged covid “makes sense” because “sometimes the viruses hide in certain cells and it is difficult to reach them.”
Will the drug be successful in killing any remaining virus?
“I don’t know,” she said. “We’ll see.”
Bill Fimbres, 67, of Mountain View, California, was Stanford’s first participant in the Paxlovid trial and received his first dose on Monday. (He won’t know if he received the real drug or a placebo until he finishes the study.)
He has been struggling with the effects of long Covid for a year and a half. He still can’t smell or taste. She has extreme fatigue, trouble keeping her balance and difficulty “thinking straight,” she said. “It’s like you have someone else’s brain.”
Fimbres has tried naltrexone, a drug that often treats addiction, to relieve his brain fog without success. Otherwise, she said, his doctors have had nothing else to offer.
“If I could get rid of just one of my symptoms, that would be great,” he said.
“I’m just going with hope.”