United States President Joe Biden on Thursday tested positive for Covid-19, White House Press Secretary Karine Jean-Pierre said.

Biden is experiencing very mild symptoms and is taking the antiviral drug Paxlovid, the press secretary said. In the United States, the medicine is used for treating mild to moderate coronavirus in persons aged 12 years and older who are at high risk for severe disease, according to CNN.

Biden is at increased risk for severe disease as he is 79 years old.

“Consistent with CDC [Centers for Disease Control and Prevention] guidelines, he will isolate at the White House and will continue to carry out all of his duties fully during that time,” Jean-Pierre said. “He has been in contact with members of the White House staff by phone this morning, and will participate in his planned meetings at the White House this morning via phone and Zoom from the residence.”

This is the first time that the president has tested positive for Covid-19. He had tested negative for the disease on Tuesday.

On Thursday morning, Biden did not have a fever, the White House’s coronavirus coordinator Ashish Jha said, according to CNN. Jha, however, said that the president has a runny nose, dry cough and some fatigue.

Biden had received his first two doses of Pfizer’s Covid-19 vaccine before taking over as president, according to the Associated Press. He got his first booster shot on September 27 and an additional booster dose on March 30.