Nothing about COVID is completely straightforward, including the wonder drugs used to treat it.
The FDA is investigating cases in which people who have taken Paxlovid — the oral antiviral drug shown to be extremely effective at reducing hospitalizations and deaths — see a recurrence of their COVID symptoms days later after completing the regimen. The phenomenon appears to be rare, and it’s not clear that Paxlovid itself has anything to do with the virus recurrence. Most accounts have been anecdotal, spreading on Twitter and other social-media sites. NBC News reported on a typical occurrence:
Michael Henry, 31, a vaccinated and boosted software engineer in Philadelphia, first got sick with Covid on April 4, suffering from chills and a fever.
Henry, who has medical conditions that raise his risk of severe disease, got a Paxlovid prescription from an urgent care center the next day. Within 48 hours, he was feeling “totally fine.” But then, one week after his last dose, he got sick once again, with milder cold-like symptoms, and remained sick for about five days.
Needless to say, such incidents complicate the guidance around isolation and when it’s permissible to return to socializing and traveling after testing negative.
Pfizer, which produces Paxlovid, said in a statement that it had documented a small number of people with post-Paxlovid recurrence of symptoms but no more than those who took a placebo.
There is no evidence that a virus mutation is behind the second round of symptoms. Rather, scientists theorize that some people need a longer course of Paxlovid than the five-day standard. Because the drug has not been officially FDA-approved, doctors can’t currently adjust the length of treatment based on their discretion.
Clifford Lane, deputy director for clinical research at the National Institute of Allergy and Infectious Diseases, told Bloomberg that the problem was “a pretty urgent thing for us to get a handle on.”
The central challenge regarding Paxlovid thus far has been logistical. Though the drug was approved months ago, it has been difficult for many patients to obtain and has often required navigating a bureaucratic thicket. Many doctors are not familiar with Paxlovid, supplies often go unused, and it has been difficult to obtain quickly in large swathes of the country — a major problem considering that it is most effective when taken during the early days of infection. The Biden administration has recently ramped up efforts to make the drug more widely available.