WASHINGTON (NewsNation Now) — The COVID-19 omicron variant is “just raging around the world,” the White House’s top medical adviser said Sunday as President Joe Biden prepares to issue “a stark warning of what the winter will look like” for unvaccinated Americans.

Dr. Anthony Fauci, the country’s leading infectious disease expert, told NBC’s “Meet the Press” that “the real problem” for the U.S. hospital system is that, “We have so many people in this country who are eligible to be vaccinated who have not yet been vaccinated.”

The prospect of a winter chilled by a wave of coronavirus infections is a severe reversal from the optimism projected by Biden some 10 months ago, when he suggested at a CNN town hall that the country would essentially be back to normal by this Christmas. 

Biden plans to speak Tuesday on the status of the fight against COVID-19 and discuss government help for communities in need of assistance, White House press secretary Jen Psaki tweeted. She also said he will be “issuing a stark warning of what the winter will look like for Americans that choose to remain unvaccinated.”

The administration is expecting a series of breakthrough infections with the surge of holiday travelers. Fauci said most people who have been vaccinated and gotten a booster should be fine if they take precautions such as wearing masks in crowded settings including airports.

“Omicron may not be as deadly as delta, we’re still seeing a lot of delta cases out there right now but the overall numbers of people infected with omicron is going to be astounding,” Dr. Kristin Englund said on “Morning in America.” “So we’re going to see a huge number of people. So even if only a small percentage of those are ill enough to get hospitalized or die, those numbers are still going to be very large. “

About one in six Americans have received their booster shot, according to data to complied the Centers for Disease Control and Prevention. More than 60% of the population has received two coronavirus vaccine doses, according to CDC data.

Englund said there is still time to get a booster for Christmas to boost your immune system before the holidays.

“Usually our boosters are not going to be as effective until about two weeks after the booster shot. But you know, it’s certainly worth getting it and trying to at least boost your immune status a little bit,” Englund said.

This comes as Sens.  Elizabeth Warren of Massachusetts and Cory Booker of New Jersey say they have tested positive for COVID-19. In separate statements Sunday, the Democrats said they had been fully vaccinated with two doses and a booster and their symptoms were mild. They also encouraged others to get the trio of shots if eligible.

Englund weighed in on “Morning with America.” You can watch the full interview in the player below.