get a good look at the virus and ramp up to fight it once the treatment ends. Or it could be that some people clear the antiviral drug from their bodies faster than others.
“If you have faster clearance, you may not have the exposure necessary to clear the virus,” says Ashley Brown, a virologist at the University of Florida in Orlando.
“We are continuing to monitor the data, but we have not seen any resistance emerge to date in patients treated with Paxlovid and believe the return of elevated detected nasal viral RNA is uncommon and not uniquely associated with treatment,” Pfizer spokesperson Kit Longley said in an email.
Q: Given the rebound effect, do current prescription guidelines need to be revisited?
Some medical experts wonder if tweaking the timing or duration of a course of Paxlovid might eliminate the rebound effect some patients experience. If people started taking Paxlovid on day 3 of symptoms, instead of right away, for example, their bodies’ defenses could kick in, bolstered by vaccines or previous infections, Nori shares.
“Then we augment with the antiviral, and this rebound might be mitigated,” she adds.
Many experts believe a five-day course is just too short, says Wachter, who wants more data. “You would think it wouldn’t be that hard to do a study on five days versus seven days versus 10 days,” he notes.
According to Pfizer’s Longley: “There may be some patient populations who may benefit from longer durations of treatment or recurrent treatment, and we are considering additional studies to evaluate this in some populations.”
Q: Fauci took a second course of Paxlovid after experiencing a rebound effect. Is that something other patients can do too?
Generally, no.
Fauci says he took a second course of Paxlovid after testing positive for COVID and feeling even sicker on the second go-around with the virus.
Prescription guidelines state clearly that “Paxlovid is not authorized for use longer than five consecutive days.”
Not all clinicians agree with the guidelines. “For people who are really high-risk, it’s hard to say, ‘Just take Tylenol,’” says Dr. David Wohl, a professor of medicine in the division of infectious diseases at the University of North Carolina-Chapel Hill.
At Brigham and Women’s Hospital, clinicians don’t generally recommend a second course of Paxlovid for patients who experience a rebound, says Kuritzkes, “though there is some diversity of opinion.”
In the FDA’s guidance to providers in May, Dr. John Farley, director of the Office of Infectious Diseases, says, “There is no evidence of benefit at this time for a longer course of treatment (e.g., 10 days rather than the 5 days recommended in the Provider Fact Sheet for Paxlovid) or repeating a treatment course of Paxlovid in patients with recurrent COVID-19 symptoms following completion of a treatment course.”
Fauci’s move was disconcerting to some clinicians.
“I was a little surprised and taken aback that the country’s top doctor went against guidance,” say Roberts, of Yale. “That sends a mixed message to me. I imagine I’ll get patients who say, ‘Dr. Fauci got two courses. Why not me?’”
Q: Are people contagious if they have a rebound? Should they isolate?
If people test positive again after a course of Paxlovid, Kuritzkes says, it’s assumed they are contagious, and they should isolate from others.
Q: Will the coronavirus become resistant to Paxlovid?
It’s a concern, experts say, but there’s no evidence it’s happened yet.
“The virus is mutating at all regions of its genome at all times, so at some point, Paxlovid will probably become less effective than when the study was done a year ago,” Roberts adds.
Paxlovid is safe and highly effective at preventing hospitalization and severe disease from COVID, however, you should consult with your doctor before taking it, especially if you are taking other medications to ensure it is safe.