The country’s top infectious disease expert, Anthony Fauci, has been struck by a phenomenon that appears to be becoming more common in the latest stage of the pandemic—rebounding bouts of COVID-19 after a course of the antiviral drug Paxlovid.
In an interview Tuesday at Foreign Policy’s Global Health Forum, Fauci recounted the progression of his infection to his current rebound, which he said has been much worse than his first round with the disease. Fauci—the director of the National Institutes of Health’s National Institute of Allergy and Infectious Diseases (NIAID) and chief medical advisor to the president—is 81 years old and has been fully vaccinated against COVID-19 and boosted twice.
He first tested positive on a rapid antigen test on June 15 and experienced “very minimal symptoms.” But his symptoms worsened and he began a five-day course of Paxlovid. “And I felt really quite well,” Fauci said, adding that he just had mild nasal congestion and fatigue. When he had finished the five-day course, he had reverted to negative on antigen tests for three consecutive days. But, “then on the fourth day—just to be absolutely certain—I tested myself again, and I reverted back to positive … and then over the next day or so I started to feel really poorly, much worse than in the first go-around.”
Fauci subsequently went back on Paxlovid for another five-day course. “Right now, I’m on my fourth day of a five-day course of my second course of Paxlovid,” he said Tuesday. “And, fortunately, I feel reasonably good, I mean, I’m not completely without symptoms, but I certainly don’t feel acutely ill.”
Conflicting treatment advice
Fauci’s second course of treatment conflicts with the stance of the US Food and Drug Administration and the Centers for Disease Control and Prevention. In a May 24 health advisory, the CDC wrote, “There is currently no evidence that additional treatment for COVID-19 is needed for COVID-19 rebound. Based on data available at this time, patient monitoring continues to be the most appropriate management for patients with recurrence of symptoms after completion of a treatment course of Paxlovid.”
Likewise, the FDA also stated in May that “there is no evidence of benefit at this time for a longer course of treatment … or repeating a treatment course of Paxlovid in patients with recurrent COVID-19 symptoms following completion of a treatment course.”
However, Albert Bourla, CEO of Pfizer, which makes Paxlovid, said that a second Paxlovid course could be used to treat rebound cases.
How and why
Beyond questions of how best to treat rebounds, it’s also unclear how common they are or why they happen. The CDC notes that resurgent symptoms of COVID-19 are not unique to people taking Paxlovid. “A brief return of symptoms may be part of the natural history of SARS-CoV-2 (the virus that causes COVID-19) infection in some persons, independent of treatment with Paxlovid and regardless of vaccination status,” the agency wrote in its health alert.
That squares with Pfizer’s initial clinical data on Paxlovid, which found that about 1 percent to 2 percent of both the treatment and placebo groups had rebounds in trials. But, with more people now taking Paxlovid, anecdotal reports of post-Paxlovid rebounds appear prevalent on social media.
Experts are also still figuring out why rebounds happen. Last week, researchers at Fauci’s NIAID reported encouraging preliminary data from a small study suggesting that rebounds are partly due to immune responses getting reignited as the body clears dead human cells and viral debris in the aftermath of a quickly smothered infection. The study found no evidence of more concerning potential explanations for rebounds, such as the possibility that SARS-CoV-2 is mutating to thwart Paxlovid or that people’s immune systems fail to protect against the virus. Moreover, limited data published by the CDC suggests that those who have a rebound do not tend to end up suffering more severe COVID-19, requiring hospitalization or emergency care.