President Joe Biden tested positive for COVID-19 after a campaign event in Las Vegas on Wednesday, the White House said.

The embattled 81-year-old Biden, who has had the illness twice previously and is fully vaccinated and boosted, was forced to cancel another Las Vegas speaking engagement as a result of his positive test.

“He will be returning to Delaware where he will self-isolate and will continue to carry out all of his duties fully during that time,” White House press secretary Karine Jean-Pierre said in a statement. “The White House will provide regular updates on the president’s status as he continues to carry out the full duties of the office while in isolation.”

Biden has taken hit after hit in the polls since his first debate against the GOP presidential nominee, former President Donald Trump, with the race further scrambled after the attempt on Trump’s life on Saturday.

A number of top Democrats have called on Biden to step aside, citing his age, apparent cognitive difficulties and the rigors of a full-blown campaign against Trump — and questions over his ability to serve a second four-year term. Rep. Adam B. Schiff, D-Calif., who is running for Senate and is an influential figure in his party with close ties to former Speaker Nancy Pelosi, D-Calif., on Wednesday became the latest senior Democrat to call for Biden to leave the race.

Jean-Pierre passed along an update from Biden’s doctor, who said he had “upper respiratory symptoms” and felt “general malaise,” along with a runny nose and cough. His symptoms are “mild” and he will be isolating at home in Rehoboth Beach, Del. He’s had a dose of the antiviral medication Paxlovid, his physician said.