WASHINGTON (AP) — A person traveling with President Joe Biden to Europe this past week received a positive test result for the coronavirus, the administration confirmed Thursday, saying the individual did not have close contact with the president.

The fully vaccinated person is asymptomatic and is remaining in Scotland to quarantine while undergoing additional tests after testing positive on a lateral flow rapid test issued by the UK government required for all attendees at the U.N. climate summit underway in Scotland. Biden tested negative for the virus on Tuesday, the White House said.

Breakthrough infections among fully vaccinated people are rare, but have occurred somewhat more frequently as the more transmissible delta variant of the virus has become the dominant strain in most of the world. The vaccines still dramatically reduce instances of serious illness and death.

The White House says out of an abundance of caution — and in a move above and beyond Centers for Disease Control and Prevention guidance — a few staff members who were in close contact with the individual did not return to the U.S. aboard Air Force One, and instead flew home on a different government plane.

Travelers with Biden on his five-day trip to Rome and Scotland were tested daily with a mix of rapid testing and more-accurate PCR tests.

The instance is not believed to be related to White House press secretary Jen Psaki’s diagnosis with COVID-19. She stayed home from the foreign trip after a member of her household tested positive for the virus. She confirmed her diagnosis publicly on Sunday saying she had “mild symptoms” and was continuing to work from home while waiting for the infection to pass.

Bloomberg first reported on the positive case.