WASHINGTON >> President Joe Biden was in close contact with a White House official who later tested positive for the coronavirus, the administration said Monday.

The president spent about 30 minutes near the official aboard Air Force One on a trip from South Carolina to Pennsylvania on Friday, Jen Psaki, the White House press secretary, said in a statement. The official, who was vaccinated and had received a booster shot, began experiencing symptoms two days later and tested positive Monday morning.

“The president is tested on a regular basis. As part of that regular testing, the president received an antigen test Sunday, and tested negative,” Psaki said. “This morning, after being notified of the staffer’s positive test, the president received a PCR test and tested negative.”

The news came as administration officials acknowledged that as the highly contagious omicron variant has surged, a cluster of cases have been reported in and around the White House, including at the National Security Council, the State Department, Treasury and other agencies. Biden, who is 79, will deliver a speech Tuesday that his advisers say is meant to emphasize that fully vaccinated people will face far fewer health risks from the virus and its variants than the unvaccinated.

“This is not a speech about locking the country down,” Psaki told reporters Monday. “This is a speech outlining and being direct and clear with the American people about the benefits of being vaccinated, the steps we’re going to take to increase access and to increase testing, and the risks posed to unvaccinated individuals.”

In her statement about Biden’s exposure to the virus, Psaki added that he would be tested again Wednesday, and that as a fully vaccinated person, he was not required to quarantine after exposure.

Researchers still do not know how likely omicron is to cause severe illness in most people, but its speed has stunned public health experts. With omicron already the dominant form of the coronavirus in the United States, White House officials have tried to emphasize that breakthrough cases among the fully vaccinated and boosted will most likely be mild compared with infections the unvaccinated may face; but given the variant’s contagiousness, those cases could become more common.

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This article originally appeared in The New York Times.