Officials with COVID who take Paxlovid keep getting rebound positives. It’s now happened with Biden, Fauci, and the CDC head

Walensky, who initially tested positive for the virus on Oct. 21, completed a course of the COVID antiviral drug and eventually tested negative. But she tested positive again Sunday after again developing mild symptoms, the agency said in a press release.

She is isolating at home and will participate in meetings virtually, the agency added.

Walensky joins a shortlist of prominent U.S. pandemic figures, including President Joe Biden and presidential physician Dr. Anthony Fauci, who’ve tested negative, then positive again after taking the popular pills, prescribed for those with documented COVID who are at high risk for severe disease.

Paxlovid has become known for its “rebound cases,” referred to by the CDC as a “brief return of symptoms.”

Such rebounds, however, can happen with or without Paxlovid, Andy Pekosz, virologist at the Johns Hopkins Bloomberg School of Public Health, recently told Fortune.

“It’s not uncommon for people to have a positive test a few days after a negative test with COVID-19,” he said. “What I think people are more focused on these days is if this may be a Paxlovid rebound, meaning he’ll have a recurrence of the virus.”

While the U.S. Centers for Disease Control and Prevention says that COVID rebounds are rare, they could be more common than we know, as most individuals with COVID stop testing after they receive a negative result.

“The White House does a very good job of testing people on a daily basis,” Pekosz said. “They’re much more likely to catch some of these rare things with that level of frequency.”