Pfizer's antiviral drug Paxlovid is currently used to prevent severe illness from Covid-19, but a few early reports suggest it may also help improve long Covid symptoms. However, researchers caution that more rigorous studies, particularly clinical trials, are needed to determine the drug's effectiveness on the chronic condition.

Case study: Recovery clinics for Covid-19 long-haulers

A potential treatment for long Covid

According to Reuters, long Covid may affect up to 30% of people infected with the coronavirus, leading some health experts to call it the "pandemic after the pandemic." Because the condition manifests in different ways in different patients, it has been difficult to pinpoint an exact cause or find an effective treatment.

However, there are now anecdotal reports and case studies suggesting that Paxlovid could also treat symptoms of long Covid in some patients, particularly those who may having lingering coronavirus material in their systems.

For example, Lavanya Visvabharathy, an immunologist at Northwestern University, experienced months of symptoms, including headaches, fatigue, and disturbed sleep, after she was first infected by the coronavirus in December 2021. She also repeatedly tested positive for months after her infection. Then, after taking Paxlovid in March, "all my symptoms went away," she said.

In addition, researchers at the University of California, San Francisco, recently published a preprint study that followed three patients who developed long-term symptoms after coronavirus infection. All three patients were in their 40s and vaccinated and boosted.

For two of the patients, they "were able to access Paxlovid antiviral therapy and feel that their long COVID symptoms improved substantially," said Michael Peluso, one of the study's authors. However, the third patient, who was taking Paxlovid to treat an acute infection, saw his symptoms rebound after initially resolving and later developed long Covid.

"There's been a lot of hope that early antiviral therapy, in addition to preventing severe COVID, will prevent long COVID," Peluso said. "And that might be true, but this case suggests that it won't be true 100% of the time."

"The key aspect of [the third patient] is that longer courses of Paxlovid may be needed, and giving it too early might not be optimal," he added. "Only by doing rigorous studies will we get answers."

Experts call for more rigorous studies on Paxlovid and long Covid

So far, scientists have cautioned that these reports are "hypothesis-generating only" and more rigorous, in-depth studies are needed to determine Paxlovid's effect on long Covid symptoms. Currently, there are fewer than 20 clinical trials testing long Covid treatments, and only a few have moved past the early stages, Reuters reports.

According to Kit Longley, a spokesperson for Pfizer, the company is "considering how we would potentially study" long Covid, but does not have any studies on the condition underway. Currently, the company is running two large clinical trials testing whether Paxlovid can prevent coronavirus infection, which "may provide us with relevant data to help inform future studies," Longley said.

In addition, NIH is currently seeking proposals for clinical trials for long Covid treatments and said it "is very interested in long term viral activity as a potential cause of PASC (long COVID), and antivirals such as Paxlovid are in the class of treatments being considered for the clinical trials."

However, some researchers note that large-scale trials of long Covid treatments are likely to be difficult. Currently, there is still no consensus on how to define or diagnose long Covid, or how to determine what metrics of improvement would look like, given the condition's various symptoms.

In addition, Paxlovid may only be beneficial to patients whose long-term symptoms are due to lingering viral remnants. Other patients whose symptoms may be due to chronic inflammation or autoimmune issues are unlikely to benefit.

Nevertheless, because long Covid patients have so few treatment options available, many are "itching for any type of treatment" even with the potential risks, said Angela Meriquez Vázquez, who runs the long Covid advocacy group Body Politic.

"The goal [of these long Covid studies] is not to cure everyone but understand who benefits," said Akiko Iwasaki, a long Covid researcher from Yale University. And Iwasaki noted that even if "it's only 10 percent of patients that respond positively," that could still mean millions of people see their long Covid symptoms improve if Paxlovid or other treatments are effective. (Wu, The Atlantic, 5/10; Walker, MedPage Today, 5/6; Steenhuysen, Reuters, 5/5; Steenhuysen, Reuters, 4/18)