Jen Psaki, Joe Biden’s White House press secretary, said on Sunday she had tested positive for Covid-19.

Psaki, 42, did not travel with Biden to Rome for this week’s G20 summit. The president is also due to travel to Glasgow for the Cop26 climate talks. Biden has been accompanied in Europe by his principal deputy press secretary, Karine Jean-Pierre.

News of a positive test for such a close aide to the president came a little over a year after an outbreak at the White House reached the then president, Donald Trump, who fell seriously ill and was forced to spend time in hospital.

In a statement, Psaki said she last saw the 78-year-old Biden on Tuesday, “when we sat outside more than 6ft apart and wore masks”.

Biden tested negative for Covid-19 on Saturday, Reuters quoted “a person familiar with the matter” as saying.

Psaki said she stayed in the US “due to a family emergency, which was members of my household testing positive for Covid-19”. She has two children.

“Since then,” Psaki continued, “I have quarantined and tested negative via PCR for Covid on Wednesday, Thursday, Friday and Saturday. However, today I tested positive for Covid.

“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 also said that “thanks to the vaccine I have only experienced mild symptoms, which has enabled me to continue working from home.

“I will plan to return to work in person at the conclusion of the 10-day quarantine following a negative rapid test, which is an additional White House requirement beyond [Centers for Disease Control and Prevention] guidance, taken out an abundance of caution.”

White House staff and others traveling with the president began undergoing daily tests for Covid-19 before departing Washington and are all fully vaccinated. Many officials have also received booster shots, due to the close-quarters environment and frequent travel associated with their work.

Biden got his Covid-19 booster on 27 September, shortly after federal regulators approved the third dose for many Americans.

On Sunday Eric Feigl-Ding, an epidemiologist and senior fellow at the Federation of American Scientists, responded to the news that Psaki had worn a mask around Biden by tweeting: “Good to still mask up, even if vaxxed.”

According to Johns Hopkins University, the US has recorded nearly 46m cases of Covid-19 and more than 745,000 deaths. Resistance to vaccination mandates remains a concern, particularly among Republican voters, though case numbers are slowing.

On Sunday, the CDC said the US had administered 422,070,099 doses of Covid-19 vaccines, up from 420,657,683 doses on Saturday. The agency said 221,520,153 people had received at least one dose, while 192,453,500 people were fully vaccinated.

The CDC tally includes two-dose vaccines from Moderna and Pfizer/BioNTech and Johnson & Johnson’s one-shot vaccine. About 18.6 million people have received a booster dose.

Full approval for children aged five to 11 to receive the Pfizer/BioNTech vaccine is expected as soon as this week.