Democratic Senators Elizabeth Warren and Cory Booker said Sunday that they had tested positive for COVID-19. Warren tweeted that she tests regularly for COVID-19, and while she tested negative last week, she tested positive on Sunday.

“Thankfully, I am only experiencing mild symptoms & am grateful for the protection provided against serious illness that comes from being vaccinated & boosted,” Warren tweeted. 

Booker said in a statement that he had experienced mild symptoms on Saturday, and he learned he tested positive on Sunday. 

“Fortunately, my symptoms are relatively mild,” the senator from New Jersey said. “I’m beyond grateful to have received two doses of vaccine and, more recently, a booster —  I’m certain that without them I would be doing much worse. I encourage everyone who is eligible to get vaccinated and boosted.”

Warren and Booker were both on the Senate floor last week for several key votes, including authorizing the Pentagon’s budget for 2022 and increasing the debt limit, which will prevent the U.S. from defaulting on its bills.

Warren’s positive test result comes amid a nationwide surge in COVID-19 cases, as fears of the fast-spreading Omicron variant cast a shadow over the holiday season. The U.S. reported more than 80,000 cases and 250 additional deaths in the past 24 hours, according to data from Johns Hopkins University.

Dr. Anthony Fauci, the nation’s leading infectious disease expert, said Sunday on NBC’s “Meet the Press” that Omicron is “just raging around the world.” 

President Biden is expected to address Americans on Tuesday amid the surge in infections.