Biden Tests Negative for Coronavirus but Will Keep Isolating

WASHINGTON — President Biden finally tested negative for the coronavirus on Saturday, a week after his rebound case emerged, but the White House physician said the president would remain in isolation “in an abundance of caution” until a second negative test.

Mr. Biden has been staying away from the Oval Office since he tested positive again on July 30, though he has tried to maintain a public presence through appearances by video from the White House residence. The recurrence of the virus has kept him off the road for political events and delayed summer vacation plans as well.

The president has experienced few symptoms during his rebound case, according to Dr. Kevin C. O’Connor, the White House physician, and he appeared in relatively good health in his video events over the last few days. “The president continues to feel very well,” Dr. O’Connor said in a memo released to reporters on Saturday.

Through the president’s initial bout with Covid-19 and during his rebound case, Dr. O’Connor has never appeared before reporters to answer questions, unlike previous White House doctors under other presidents. The White House has never offered a clear explanation about why. Dr. O’Connor’s daily memos have provided no theories about where and how the president was infected. White House officials have said that those deemed to have been in close contact with Mr. Biden all tested negative.

The president was treated with Paxlovid early in his bout with Covid, and while the drug has been credited with great success in suppressing the virus and preventing severe cases and hospitalizations, a number of patients who have taken it have nonetheless tested positive again a few days after the last dose of the five-day regimen.

Initial clinical studies found that only about 1 percent to 2 percent of those treated with Paxlovid, which is made by Pfizer, experienced symptoms again. Subsequent studies of patients have found higher rates, though still in the single digits.

But some doctors and patients have speculated that the rebound rate could be even higher because of anecdotal experiences and because of the characteristics of the highly contagious Omicron subvariants in circulation this summer. Among those who have had a rebound case after taking Paxlovid was Dr. Anthony S. Fauci, the president’s chief medical adviser and a leading figure in the response to the pandemic.

Mr. Biden has been described by aides as eager to get out of isolation and back on the road as the midterm congressional campaign begins to heat up. As a result of his infection, he has had to cancel a number of planned trips and has limited his contact with aides, advisers and others at a time when he has scored some important victories that he would like to promote.

“I wish I were with you in person, quite frankly,” he told Vice President Kamala Harris and several cabinet members over a video feed during an event on Wednesday describing his plans to take action to protect abortion rights. “But I’m getting there.”