Biden has tested positive for COVID yet again in case of Paxlovid rebound

U.S. President Joe Biden has tested positive for COVID yet again in what a White House physician calls a case of Paxlovid rebound—this after testing negative Tuesday evening and Wednesday morning, when he exited isolation, in addition to Thursday and Friday mornings.

The president will resume isolation despite not experiencing new symptoms, he said in a Saturday tweet.

“Folks, today I tested positive for COVID again,” he wrote. “I’ve got no symptoms, but I am going to isolate for the safety of everyone around me.”

“I’m still at work, and will be back on the road soon.”

Biden, 79, is one of millions of Americans who have recently tested positive for Omicron subvariant BA.5, as confirmed last week by his personal physician, Dr. Ashish Jha. His initial positive test came July 21, after a week of traveling across the Middle East. He tested negative for the virus on Tuesday night and again on Wednesday morning of this past week, when he ended his isolation, according to the Associated Press.

He additionally tested negative Thursday and Friday mornings, according to a Saturday letter from presidential physician Dr. Kevin O’Connor to White House Press Secretary Karine Jean-Pierre.

“The president tested positive late Saturday morning, by antigen testing,” O’Connor wrote. “This in fact represents ‘rebound’ positivity.”

There is no reason to resume treatment, he wrote, adding that the president will continue to be monitored.

What is Paxlovid?

The president was treated with the COVID-19 antiviral Paxlovid the day he was diagnosed, according to multiple news outlets. It’s a pill approved for treatment of COVID-19 in high-risk adults and has emergency-use authorization from the U.S. Food and Drug Administration.

But the drug is known for “rebound” cases, referred to by the U.S. Centers for Disease Control and Prevention as “a brief return of symptoms.”

When diagnosed with COVID in June, chief presidential medical adviser Dr. Anthony Fauci was prescribed the antiviral due to his advanced age, which put him at greater risk for a severe outcome from COVID, despite being fully vaccinated and twice boosted.

Fauci later said he had experienced a Paxlovid rebound.

“After I finished the five days of Paxlovid, I reverted to negative on an antigen test for three days in a row,” Fauci, 81, said during an event at Foreign Policy’s Global Health Forum, Bloomberg reported. “And then on the fourth day, just to be absolutely certain, I tested myself again.”

“I reverted back to positive,” he said. 

Fauci later told the New York Times that Paxlovid kept him out of the hospital and stopped his infection from becoming more severe initially, saying, “Paxlovid did what it was supposed to do.”

Fauci began a second course of Paxlovid when symptoms emerged “much worse than the first go-around,” he said. In May the CDC issued a health advisory about such rebounds, saying there was no evidence that additional treatment is needed for rebound cases. It is unclear why Fauci apparently acted against CDC advice.

In June, Pfizer, which manufactures Paxlovid, announced that it would stop adding new participants to a trial of the drug among COVID patients at low risk of hospitalization and death. The study failed to demonstrate that the drug reduced symptoms, or hospitalizations and deaths in a statistically significant way, according to Bloomberg.

How long to quarantine?

The CDC currently advises COVID-positive individuals to quarantine for five days before returning to normal life (and masking in public for an additional five days). The recommended isolation time was 10 days until December, when the federal health agency halved its recommendation.

But “there is not data to support five days or anything shorter than 10 days,” Amy Barczak, a physician at the Massachusetts General Hospital Infectious Disease Division, recently told Nature.

Scientists have questioned the scientific rationale behind the policy since the CDC introduced it late last year. And now critics have more data to back up their claims: Viral shedding can occur beyond 10 days in even healthy, vaccinated adults, according to a preprint out of London published this month.

Some scientists advise that people should stop quarantining only once they test negative using at-home tests, rather than relying on the CDC’s five-day rule.

Biden did so, however, testing negative at five and then six days after infection before ending his quarantine, during which he worked from home. The White House had said that Biden would go “above and beyond” the CDC’s five-day guidance and wait until he tested negative before returning to public life.