President Biden, Vice President Harris and their spouses were in close contact with a White House official who soon afterward tested positive for COVID-19, White House press secretary Jen Psaki disclosed in a statement Monday. Mr. Biden was tested on Sunday with an antigen test and was negative. After he was informed of the staff member's positive test, the president took a PCR test and again tested negative. He'll take his next test on Wednesday. The CDC's guidance doesn't demand fully vaccinated individuals to quarantine after they're exposed to COVID-19, so, the president will continue with his daily schedule, Psaki said. She described the official as a "mid-level staff member" who doesn't regularly have contact with Mr. Biden. The official received a positive COVD-19 test on Monday morning, three days after spending about 30 minutes in Mr. Biden's proximity on Air Force One en route Philadelphia from South Carolina. The staff member is fully vaccinated, had received a booster shot and tested negative before boarding Air Force One. The official didn't start to experience symptoms until Sunday. Psaki said those who were in close contact with the official on Air Force One are being contacted and advised to take a COVID-19 test, in accordance with Centers for Disease Control and Prevention guidance. The president's exposure occurred as the highly transmissible Omicron variant overtook the Delta variant as the most dominant strain of COVID-19 in the U.S., according to new data released by the CDC on Monday. The variant now makes up more than 73% of new infections, a nearly six-fold increase compared to the week before. Omicron makes up the highest share of new cases in the South, Central Midwest, Pacific Northwest, and the New York area. Max Bayer contributed to this report.