U.S. Sen. Elizabeth Warren said Sunday she has tested positive for COVID-19 as the country deals with another surge in cases and the emergence of the omicron variant.

The Massachusetts Democrat tweeted she's vaccinated, has received her booster shot and is experiencing mild symptoms in a breakthrough case of the virus.

“Thankfully, I am only experiencing mild symptoms & am grateful for the protection provided against serious illness that comes from being vaccinated & boosted,” she wrote, using the occasion to also urge anyone not vaccinated to do so.

Warren didn’t elaborate on where she might have contracted the virus but said she's regularly tested and turned up negative for COVID-19 earlier this week. Spokespersons for her office didn't respond to an email seeking comment Sunday.

Congress was on recess Monday for the holidays, but many lawmakers were in Washington last week meeting with colleagues and others on Capitol Hill.

Sen. Cory Booker of New Jersey and U.S. Rep. Jason Crow of Colorado also announced Sunday that they have tested positive for COVID-19.

Booker, in a statement from his office, 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.”

Crow said he is fully vaccinated and got a booster shot and is experiencing only mild symptoms.