President Joe Biden tested positive for Covid-19 on Saturday after several days of testing negative, marking the second time Biden tested positive for the virus this year.

White House physician, Dr. Kevin O’Connor said in a memo to Press Secretary Karine Jean-Pierre that the president is feeling fine, but given the positive antigen test, he will reinitiate isolation procedures.

“The President has experienced no reemergence of symptoms, and continues to feel quite well,” Dr. O’Connor wrote. “However, given his positive antigen test, he will reinitiate strict isolation procedures.”

The President tested negative for four consecutive days, but according to Dr. O’Connor, Biden is experiencing “rebound COVID positivity in a small percentage of patients treated with Paxlovid,” Pfizer’s antiviral oral pill.

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Biden first tested positive for Covid-19 on July 21, Benzinga reported. He returned to the Oval Office five days later, and continued to work during his initial isolation phase.

Photo: Courtesy of National Renewable Energy Lab on flickr