When Dr. Anthony Fauci caught Covid in June, he took Paxlovid, an antiviral drug for people with mild to moderate symptoms whose age or immune status puts them at high risk for serious illness. The treatment consists of three pills taken twice a day for five days.
Fauci completed treatment and tested negative for Covid. But about three days later, a test came back positive again. His symptoms – runny nose, sore throat and fever – also resurfaced.
A small minority of people who take Paxlovid see a similar rebound effect.
“When you look at the studies, it usually doesn’t happen very often,” Fauci, who heads the National Institute of Allergy and Infectious Diseases and is President Joe Biden’s chief medical adviser, said Tuesday on “Morning Joe from MSNBC. But he noted there have been “anecdotal cases” that suggest rebounds are more common now than they were in clinical trials.
About 1% to 2% of people taking Paxlovid in Pfizer’s clinical trial tested positive for coronavirus after testing negative. Rebound rates are around 5% among the tens of thousands of people who have taken the drug under real-world conditions, White House Covid response coordinator Dr Ashish Jha told a conference. press last week.
“If you look at Twitter, you feel like everyone bounced back,” Jha said. “But it turns out that there is actually clinical data.”
A small study in June found that less than 1% of Covid patients saw their symptoms rebound about nine days, on average, after taking Paxlovid. In a larger study of 13,600 Covid patients, which has not been peer-reviewed, 6% saw their symptoms rebound within a month of treatment.
Dr Aditya Shah, an infectious disease specialist at the Mayo Clinic who led the small study, said it was difficult for people to self-diagnose rebound cases. Ideally, people would have proof that they tested positive, then negative, then positive again, he said.
The actual number of rebound cases “could be as high as 5-10%, but I don’t think it’s as common as the general community makes it out to be,” Shah said.
The Centers for Disease Control and Prevention said in May that symptoms usually rebound two to eight days after stopping Paxlovid, if they come back.
People who continue to test positive may still be contagious, which is why the CDC recommends people resume isolation for at least five days if their illness comes back.
Treatment may not be long enough
Some disease experts suspect the Paxlovid regimen is too short to clear the virus in some people.
“One of the theories is that your natural immunity just can’t kick in fast enough because you have to treat within five days of having symptoms, so it’s pretty early in the course” of the disease, said the Dr. Peter Gulick, an associate. professor of medicine at Michigan State University.
When someone takes Paxlovid, “it probably drops that viral load to a point where the body clinically doesn’t react to it with any kind of inflammation,” Gulick said. This would explain why the symptoms initially disappear in about five days.
But some people may still have lingering virus in their body, particularly if they had high viral loads to begin with or if the virus has spread to areas that drugs cannot easily reach. In this case, the symptoms could reappear.
“There might even be reservoirs,” Gulick said. “We don’t know Paxlovid’s ability to enter certain small areas of the body where the virus may be found.”
Shah, however, is not sure if extending treatment is beneficial for patients: “I would be hesitant to say now, ‘Yes, of course, take 10 days of treatment’, because that has no evidence. supporting.”
Disease experts have said it’s possible that older or immunocompromised people are more likely to have their symptoms rebound or test positive again after taking Paxlovid, but there aren’t any good ones yet. data to support the theory.
In all cases, rebound symptoms should be mild. A June CDC study found that less than 1% of people taking Paxlovid were admitted to the hospital or emergency department for Covid within five to 15 days of stopping treatment.
“Paxlovid works very well and prevents serious diseases whether they rebound or not,” Jha said last week. “That’s why the president took it.”
Biden completed his five-day course on Paxlovid on Monday. Experts said he should find out if his symptoms have rebounded in the next few days.