White House spokeswoman Jen Psaki said Sunday she has tested positive for Covid-19, after deciding not to travel to Europe with US President Joe Biden when members of her family contracted the virus.

Psaki said in a statement that though she had tested negative several times last week, her test came back positive on Sunday.

"While I have not had close contact in person with the president or senior members of the White House staff since Wednesday – and tested negative for four days after that last contact -- I am disclosing today's positive test out of an abundance of transparency," Psaki said in a statement.

"I last saw the president on Tuesday, when we sat outside more than six feet apart, and wore masks."

Psaki said she had mild symptoms, for which she credited the Covid-19 vaccine, and said she was working from home. She added that she would quarantine for 10 days before taking another test and eventually returning to the White House.

Biden, 78, was in Rome on Sunday for the G20 summit and will be in Glasgow on Monday for the COP26 climate summit. He received a Covid-19 vaccine booster shot in September.

Many Americans are still resisting vaccinations, with only 58 percent of the population fully immunized. The United States has recorded more than 745,000 deaths from Covid-19.

US health authorities have approved booster shots of the Moderna, Pfizer and Johnson & Johnson vaccines.