Biden experienced "rebound positivity" after taking Paxlovid.
President Joe Biden tested negative for COVID-19 on Saturday after experiencing a rebound infection but will continue to isolate until he gets a second negative result, the White House physician said.
"The President today continues to feel very well," Dr. Kevin O'Connor said in a letter to White House press secretary Karine Jean-Pierre. "Given his rebound positivity which we reported last Saturday, we have continued daily monitoring. This morning, his SARS-CoV-2 antigen testing was negative."
"In an abundance of caution, the President will continue his strict isolation measures pending a second negative test as previously described," O'Connor added.
Biden first tested positive for the virus on July 21, experiencing a slight fever, cough and sore throat among other mild symptoms. He isolated at the White House residence and completed a five-day course of Paxlovid, an antiviral treatment for those with mild to moderate symptoms who are considered a high risk for severe illness, before testing negative.
After emerging from isolation, he hailed the available COVID-19 vaccines and treatments.
"We've got through COVID with no fear -- I got through it with no fear. A very mild discomfort because of these essential, lifesaving tools," he said in a Rose Garden speech. "And guess what? I want to remind everybody: They are free. They are convenient. And they are safe, and they work."
But on July 30, he tested positive again in what O'Connor called an example of "rebound positivity" from the Paxlovid treatment.
While uncommon, some patients who take Paxlovid can test positive again after finishing the treatment course but doctors emphasize that doesn't mean the drug isn't effective. High-risk patients who take the antiviral treatment still have a dramatically lower risk of being hospitalized due to the virus.
Biden said he was feeling well and made several virtual appearances during his second infection, addressing the nation from the Blue Room balcony about the killing of al-Qaeda leader Ayman al-Zawahiri on Monday and touting a strong jobs report and movement on his agenda in the Senate on Friday.
Biden and first lady Jill Biden have plans to travel to Kentucky on Monday, the White House previously announced, in what would be his first trip since his diagnosis. If they do travel, they will join Gov. Andy Beshear and his wife Britainy Beshear in a meeting with families affected by the state's devastating flooding. At least 37 people died in the flooding, which also left water and electricity systems heavily damaged.