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Biden continues to test positive for coronavirus in ‘rebound’ case

President Biden had resumed activities last week after testing negative. (Demetrius Freeman/The Washington Post)

President Biden continued to test positive for the coronavirus Sunday, a day after being diagnosed with a “rebound” case, his physician said.

In a new memo released Sunday, the president’s physician, Kevin O’Connor, said Biden’s latest positive antigen test was not surprising.

“The President continues to feel well,” O’Connor wrote, adding that Biden will work out of the Executive Residence while he continues his isolation.

Biden, 79, first tested positive for the coronavirus on July 21, a Thursday, and began taking Paxlovid, an antiviral therapy that has proved highly effective in tackling coronavirus symptoms. After the president’s original positive test result, O’Connor said Biden — who is fully vaccinated against the coronavirus and has received two booster shots — should respond well to Paxlovid, “as most maximally protected patients do.”

After daily monitoring, Biden tested negative the following Tuesday evening. He emerged from his covid-19 isolation last Wednesday with a speech in the Rose Garden touting his relatively short isolation and mild symptoms as a testament to his administration’s progress on the pandemic. He urged people to take advantage of vaccine boosters, antivirals and at-home tests as well.

Biden tested negative last Wednesday morning, Thursday morning and Friday morning, before testing positive again Saturday morning using an antigen test. Biden and his doctor said he was experiencing no symptoms during the rebound infection.

What to know about rebound cases after Paxlovid treatments

Biden removed his mask for some of the events last week. White House press secretary Karine Jean-Pierre said Biden was still in compliance with guidelines from the Centers for Disease Control and Prevention because he was more than six feet apart from others.

The CDC recommends people isolate for five days after testing positive for the coronavirus and wear a mask for an additional five days when around others. Some experts have said the guidance could cause people to return to work or leave isolation when they are potentially still infectious.

Physicians have warned that people who receive the antiviral medication Paxlovid can experience “rebound” infections days after initially testing negative, although data on the frequency of the occurrence and its long-term effects remain unclear.

Initial clinical studies suggested that only about 1 percent to 2 percent of those treated with Paxlovid had symptoms again, but another study published in June reported that 6 percent experienced symptoms again. Studies are underway to determine whether a longer course of Paxlovid can help prevent rebound cases.

The CDC issued an advisory in May amid concerns about the phenomenon, recommending that people who experience a resurgence of covid-19 following treatment should again isolate for five days and wear a mask for 10 days.

The CDC recommends that the public should report rebound cases after a course of Paxlovid to Pfizer, the manufacturer of the drug.

In his memo Sunday, O’Connor wrote that Biden would continue his “strict isolation measures.”

Biden has canceled planned trips to his home in Wilmington, Del., on Sunday and to Hemlock, Mich., on Tuesday for an event in support of a bill that includes $52 billion to subsidize computer chip manufacturing and research and counter China’s influence, known as the Chips and Science Act. The legislation passed both chambers of Congress last week and is awaiting Biden’s signature. It was unclear whether Biden would participate in Tuesday’s event remotely.

Bryan Pietsch contributed to this report.