‘Rebound positivity’ lands President Biden back in isolation

President Joe Biden, who tested positive for a rebound case of COVID-19 Saturday morning, is continuing strict isolation at the White House after “unsurprisingly, his SARS-CoV-2 antigen testing remained positive,” says a letter from White House physician Kevin O’Connor.

The letter released by the White House adds that the US President “continues to feel well” and “will continue to conduct the business of the American people from the Executive Residence.”

Dr. O’Connor wrote a letter on Saturday addressed to White House Press Secretary Karine Jean-Pierre that, after testing negative multiple times beginning Tuesday evening, double-vaccinated and double-boosted President Biden tested positive again. Since he feels well and no COVID symptoms had reemerged, President Biden will not restart treatment for COVID-19.

After testing positive for the first time on July 21, as we previously reported, he completed a five-day course of Paxlovid during his five-day isolation.

Rebound COVID positivity

President Biden increased his testing cadence due to the potential for so-called COVID “rebound” positivity. This has been detected in a small percentage of patients treated with the Pfizer anti-viral medication Paxlovid.

Although only a small minority of people who take Paxlovid see such a rebound effect, the Centers for Disease Control and Prevention (CDC) issued a health advisory in May warning of the possible recurrences.

“A brief return of symptoms may be part of the natural history of SARS-CoV-2 infection in some persons, independent of treatment with Paxlovid and regardless of vaccination status,” the CDC’s Health Advisory noted. COVID-19 rebound occurs “between 2 and 8 days after initial recovery.” It is characterized by symptom recurrence “or a new positive viral test after having tested negative.”

In Pfizer’s clinical trials, around 1% to 2% of people taking Paxlovid tested positive for the coronavirus after having tested negative. However, White House COVID Response Coordinator Dr. Ashish Jha pointed out last week that rebound rates are around 5% among patients who’ve taken the drug in real-life settings.

Researchers at the University of California San Diego School of Medicine said in a June study that “the COVID-19 rebound appears to have been the result of insufficient exposure to the drug” rather than being caused “by the development of resistance to the drug or impaired immunity against the virus.”

San Francisco Chronicle recently reported Pfizer and the FDA are tracking rebound cases for further study, noting “providers and patients can report cases to Pfizer’s and the FDA’s respective adverse event reporting systems.

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