Biden, 79, says he's 'feeling fine' after testing positive for COVID AGAIN and goes back into isolation as doctors warn more than 40% o

President Joe Biden has tested positive for COVID-19, sending him back into isolation just three days after he was tested negative and was cleared to resume his duties

Biden's physician, Dr. Kevin O'Connor, said the president is experiencing no new symptoms and 'continues to feel quite well' after he tested negative on Tuesday, Wednesday, Thursday and Friday

The doctor had warned that Biden could test positive again due to a 'rebound' that can occur to elderly patients who take the Paxlovid anti-COVID drug

Despite early studies suggesting that the reinfection rate was a mere 1-2%, more recent studies put that number up around 40%

The drug is believed to be the most effective treatment against the virus, but the CDC has warned recipients of Pfizer 's antiviral COVID pill may have their symptoms rebound after they complete a course of the drug

Biden tweeted three times after Saturday's announcement, demonstrating that he is 'feeling fine and everything is good' and he is 'still at work'

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