Sen. Elizabeth Warren (D-Mass.) and Sen. Cory Booker (D-N.J.) said in separate statements Sunday that they have both tested positive for COVID-19, despite being fully vaccinated, including a booster shot. 

“I regularly test for COVID & while I tested negative earlier this week, today I tested positive with a breakthrough case,” Warren tweeted, adding that her symptoms are mild and she is “grateful for the protection provided against serious illness that comes from being vaccinated & boosted.” Booker said his case is “relatively mild” and he’s “beyond grateful to have received two doses of vaccine and, more recently a booster,” and “certain that without them I would be doing much worse.”

“Though it is unclear which coronavirus variant infected Warren and Booker, their positive tests come as top government health officials are warning that the United States will probably see record numbers of coronavirus cases and hospitalizations with the rapid spread of the new Omicron variant,” The Washington Post reports.

National Institutes of Health Director Francis Collins told CBS’s Face the Nation Sunday that the U.S. could soon see a million new cases a day of the Omicron variant, far surpassing the previous record of about 250,000 new cases a day last January. 

White House coronavirus response coordinator Jeff Zients said in a briefing Friday that while “the Omicron variant is more transmissible and our medical experts anticipate it will lead to a rise in cases,” this year we “have the power to protect ourselves” with vaccines and booster shots. 

“If you are vaccinated, you could test positive,” Zients added. “But if you do get COVID, your case will likely be asymptomatic or mild. We are intent on not letting Omicron disrupt work and school for the vaccinated. You’ve done the right thing, and we will get through this. For the unvaccinated, you’re looking at a winter of severe illness and death for yourselves, your families, and the hospitals you may soon overwhelm.”