ROME/WASHINGTON -- White House press secretary Jen Psaki tested positive for COVID-19 on Sunday, she said in a statement, adding she had last seen President Joe Biden on Tuesday.

Psaki, 42, who stated she was vaccinated and experiencing mild symptoms, said she and the president sat outside more than 6 feet (1.8 m) apart and wore masks on Tuesday. Biden tested negative for COVID-19 on Saturday, said a person familiar with the matter.

“I am disclosing today’s positive test out of an abundance of transparency,” Psaki said.

Psaki, the main spokesperson for the White House, is the most high-profile person in the Biden administration known to have contracted COVID-19 since he took office in January.

Psaki decided not to join Biden on his trip to Rome and Glasgow this week because a member of her household tested positive for the virus, after which she quarantined, she said.

She has been in quarantine since Wednesday and repeatedly tested negative before testing positive on Sunday, she said.

Psaki planned to return to work at the end of a 10-day quarantine period following a negative rapid COVID-19 test, she said in the statement.

The White House has been struggling to get the pandemic under control, with millions of Americans declining to take life-saving vaccines.

Psaki said earlier this year that Biden, who is fully vaccinated, is tested randomly every two weeks as surveillance, at the request of his physician, Kevin O'Connor. Biden, 78, has received three Pfizer Inc/BioNTech COVID-19 shots, including a booster last month.

The White House has declined to disclose the number of breakthrough COVID-19 infections that have occurred among staff.

Biden's predecessor, Donald Trump, eschewed masks and played down the seriousness of the virus in its early stages. He contracted COVID-19 in the waning stages of the 2020 presidential campaign and many of his staff, including former press secretary Kayleigh McEnany, came down with the illness.