WASHINGTON — Vice President Mike Pence was self-isolating Sunday after an aide tested positive for the coronavirus last week, but he planned to return to the White House on Monday.

An administration official said Pence was voluntarily keeping his distance from other people in line with guidance from the Centers for Disease Control and Prevention. He has repeatedly tested negative for COVID-19 since his exposure but was following the advice of medical officials.

His action came after three of the nation's top scientists took their own protective steps following possible exposure to a White House staffer infected by the coronavirus.

"Vice President Pence will continue to follow the advice of the White House Medical Unit and is not in quarantine," spokesman Devin O'Malley said Sunday. "Additionally, Vice President Pence has tested negative every single day and plans to be at the White House tomorrow."

Pence has been at home since returning to Washington from a day trip to Iowa on Friday and did not appear at President Donald Trump's meeting with military leaders Saturday at the White House. Pence was informed of the aide's positive test shortly before departing for that trip.

An official initially said Pence planned to continue working from home, before Pence's office clarified that he planned to work from the White House on Monday. It was not immediately clear how Pence's steps to self-isolate would impact his professional or public engagements.

Pence has led the White House coronavirus task force for more than two months. Top officials who have gone into quarantine because of exposure to a person at the White House who tested positive for the virus are Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases; Dr. Robert Redfield, director of the CDC; and the commissioner of the Food and Drug Administration, Dr. Stephen Hahn.

Pence's press secretary, Katie Miller, tested positive for the coronavirus on Friday, making her the second person who works at the White House complex known to test positive for the virus this week.

A military service member who acts as a valet to the president tested positive on Thursday, the first known instance where a person in close proximity to the president at the White House had tested positive.

After Miller was identified as having tested positive, Trump said he was "not worried" about the virus spreading in the White House. Nonetheless, officials said they were stepping up safety protocols for the complex.

The three other task force members have indicated varying plans for dealing with their exposure. None has announced testing positive for the virus and, taking into account what has been described as limited exposure to the infected person, are considered at relatively low risk for infection.

Fauci's institute said he was "taking appropriate precautions" to mitigate the risk to others while still carrying out his duties, teleworking from home but willing to go to the White House if called. Officials said both Redfield and Hahn will be self-quarantining for two weeks.

The three officials were expected to testify by videoconference before a Senate health committee on Tuesday. On Sunday night, the office of the chairman of the committee, Sen. Lamar Alexander, R-Tenn., announced that the senator would be self-quarantining in Tennessee for two weeks after a staff member tested positive for COVID-19. Alexander too will participate in the hearing by videoconference.