U.S. President Joe Biden tested negative for COVID-19 on Saturday in the process of his recovery from a "rebound" case, White House physician Kevin O'Connor wrote in an update.Biden feels "very well" but will continue to isolate pending a second negative testing result, said O'Connor.Fully vaccinated and twice boosted, Biden first tested positive for COVID-19 on July 21, leading to days of isolation and treatment at the White House before receiving negative testing results.He tested positive again on July 30 in a "rebound" case and had a mild cough but didn't resume treatment.Biden remains positive for COVID-19 but 'continues to feel well': doctorBiden tests positive for COVID-19 in 'rebound' case: physicianU.S. President Joe Biden tested negative for COVID-19 on Saturday in the process of his recovery from a "rebound" case, White House physician Kevin O'Connor wrote in an update.Biden feels "very well" but will continue to isolate pending a second negative testing result, said O'Connor.Fully vaccinated and twice boosted, Biden first tested positive for COVID-19 on July 21, leading to days of isolation and treatment at the White House before receiving negative testing results.He tested positive again on July 30 in a "rebound" case and had a mild cough but didn't resume treatment.Biden remains positive for COVID-19 but 'continues to feel well': doctorBiden tests positive for COVID-19 in 'rebound' case: physician