In accordance with guidelines from the Centers for Disease Control and Prevention, Biden will enter self-isolation again for at least five days. He will self-isolate at the White House until he tests negative. The agency says most rebound cases remain mild and no serious illnesses during this period have been reported.

Much like when Biden first tested positive, the White House sought to show he was still working. The president tweeted a photo of himself in a mask and without a tie, which showed him signing a statement that added individual assistance to flood survivors in Kentucky.

The president followed up by tweeting a 12-second video of himself on a White House balcony with his dog, Commander.

“I feel good, everything is fine,” Biden said, a pair of aviator sunglasses in hand. “But Commander and I have a little work to do.”

The president also took the time on Saturday to have a FaceTime conversation with people camping outside the U.S. Capitol who are seeking health benefits for military veterans exposed to toxic substances from burning fireplaces while on duty, according to White House Chief of Staff Ron Klain. A bill to expand benefits failed to clear the Senate on Wednesday. Veterans Affairs Secretary Denis McDonough brought the group’s pizza and the phone connection to speak with the president.

“Feeling better,” a band member told Biden in a video of the call posted on Twitter. Later, in a tweet, the president said he had planned to meet families on Capitol Hill but his positive test “got in the way.”

Biden’s positive test came — he had been negative Friday morning — just two hours after the White House announced a presidential visit to Michigan next Tuesday to highlight the passage of a bill to promote domestic manufacturing of high technology. Biden was also due to travel to his home in Wilmington, Delaware, on Sunday morning, where first lady Jill Biden was staying while the president tested positive. Both trips were canceled as Biden returned to solitary confinement.

Biden, 79, was treated with the antiviral drug Paxlovid after first testing positive on July 21. He tested negative for the virus last Tuesday and Wednesday. He was then allowed to leave solitary confinement while wearing a mask inside. His positive tests put him among the minority of those prescribed the drug to experience a rebound case of the virus.

White House COVID-19 coordinator Dr. Ashish Jha told reporters on Monday that the data “suggests that between 5 and 8 percent of people have rebounded” after treatment with Paxlovid.

“Recognizing the potential for so-called ‘rebound’ COVID positivity seen in a small percentage of patients treated with Paxlovid, the President has increased his testing cadence, to protect those around him and ensure early detection of any replication returns viral,” O’ Connor wrote in his letter.

O’Connor cited negative tests for Biden from Tuesday evening, Wednesday morning, Thursday morning and Friday morning, before Saturday morning’s positive antigen test result. “It actually represents ‘rebound’ positivity,” he wrote.

According to the CDC, people with rebound COVID should self-isolate for at least five days, which ends if the fever has resolved for 24 hours without medication and symptoms have improved. The patient “should wear a mask for a total of 10 days after the onset of rebound symptoms. Some people continue to test positive after day 10, but are considerably less likely to shed infectious virus.

The Food and Drug Administration and Pfizer point out that 1-2% of people in Pfizer’s original Paxlovid study saw their virus levels rebound after 10 days. The rate was about the same in people taking the drug or the dummy pills, “so it’s not clear at this point whether it’s related to the drug treatment,” according to the FDA.

As Biden tested negative, he resumed hosting in-person indoor events and meetings with White House staff and wore a mask, per CDC guidelines. But the president removed his mask indoors during his remarks on Thursday and during a meeting with CEOs at the White House complex.

When asked why Biden seemed to be breaking CDC protocols, publicist Karine Jean-Pierre said, “They were socially distant. They were quite far apart. So we made sure they were together safely on that stage.

Regulators are still studying the prevalence and virulence of rebound cases, but the CDC in May warned doctors that it had been reported to occur within two days to eight days after an initial test negative for the virus.

“The limited information currently available from case reports suggests that people treated with Paxlovid who experience COVID-19 rebound have had mild disease; there are no reports of serious illness,” the agency said at the time.

When Biden was initially released from solitary confinement on Wednesday, O’Connor said the president would “increase his testing cadence” to catch any potential virus rebounds.

Paxlovid has been shown to significantly reduce serious illness and death in those most vulnerable to COVID-19. US health officials have encouraged people who test positive to see their doctor or pharmacist to see if treatment should be prescribed, despite the risk of rebound.

Biden is fully vaccinated, having received two doses of the Pfizer coronavirus vaccine shortly before taking office, a first booster in September and an additional dose on March 30.

While patients who recovered from previous variants of COVID-19 tended to have high levels of immunity against future reinfection for 90 days, Jha said the BA.5 subvariant that infected Biden s proved to be more “immuno-evasive”.

“We have seen many people become reinfected in 90 days,” he said, adding that authorities do not yet have data on how long those who have recovered from the BA.5 strain are protected against it. reinfection.