Joe Biden has tested negative for COVID-19 a second time, after experiencing a “rebound” case last week. The president, who received both vaccine doses and a booster, first tested positive on July 21 and experienced mild symptoms. He exited isolation on July 27, after testing negative, but re-entered after testing positive again on the 30th. Rebound cases such as this have not been extensively studied, but have been attributed to the antiviral drug Paxlovid, which Biden took. He will remain in isolation until he tests negative again, the White House physician said. She added that he continues to feel “very well.”