President Joe Biden, just four days before Christmas, sought Tuesday to convince a country craving a normal holiday season that a largely unknown COVID-19 variant will not undo two years of pandemic progress.

“Are we going back to March 2020?” Biden said as the omicron variant threatens to deluge hospitals with sick patients. “The answer is absolutely no.”

Biden sought to draw a clear contrast when describing how the omicron surge will affect the vaccinated versus the unvaccinated, issuing a dire warning to 60 million unvaccinated Americans.

“How concerned should you be about omicron, which is now the dominant variant in this country and it happened so quickly. The answer is straightforward: If you’re not fully vaccinated, you have good reason to be concerned,” he said. “Almost everyone who has died in the past many months has been unvaccinated.”

Biden warned of a potentially large rise in cases among those who have not received their jabs, but said those Americans who have been vaccinated would be protected from the most severe outcomes — especially if they receive a booster.

Flanked by two Christmas trees, the president did not touch on limiting exposures through gatherings or travel during the holidays. That lack of messaging is likely to rankle public health experts concerned about omicron’s explosive growth, which could be accelerated by holiday gatherings.

The speech came as many health experts are warning the U.S. will see a rapid spike in cases that could impact several regions of the country at once. The omicron variant is highly infectious and evades some antibodies.

New Centers for Disease Control and Prevention data suggest omicron grew to comprise 73 percent of cases in the U.S. within just two weeks.

Biden outlined plans to send medically trained military personnel to hospitals this winter as they prepare for the possibility the omicron variant could drive one of the darkest chapters of the pandemic yet.

Biden announced the deployment and other steps to shore up hospitals threatened with a surge in cases driven by the omicron variant first outlined in a policy memo shared with reporters Monday night.

The federal government will also purchase half a billion rapid tests to be available beginning in January, and will once again tap the Federal Emergency Management Agency to stand up vaccination clinics, as Biden faces a race against the omicron variant spreading like wildfire across the United States — and a possible growing death toll that has already outpaced the pandemic’s first year.

Following his lengthy prepared remarks, he also responded to a reporter’s question about why more government-provided rapid tests won’t be available until after the holidays. That comes amid reports of long lines for tests snaking around several blocks and pharmacy after pharmacy sold out of take-home tests.

Some press reports have indicated that the Biden administration passed on health advisers’ recommendations to purchase tests earlier because they believed the move was expensive and that greater consumer demand would spur greater supply through free market forces.

Biden said the steep rise of omicron was unpredictable, rejecting a reporter’s premise that the initial decision to not buy millions of new test kits was a “failure.”

“What took so long is that it didn’t take long at all. What happened is the omicron virus spread more rapidly than anybody thought,” Biden replied. “If I told you four weeks ago it would spread by 50 percent, 100 percent, 200 percent you would have looked at me and said, ‘Biden what are you drinking?'”

Biden twice mentioned former President Donald Trump, who said this week he has received his booster shot. The referrals to Trump amounted to a plea to the millions of vaccine-skeptical Americans most at risk this winter who did not vote for him to get the jab because the former president has gotten three doses and oversaw vaccine development.

“Omicron is serious, potentially deadly business for unvaccinated people,” Biden said. “Thanks to the prior administration and our scientific community, America is one of the first countries to get the vaccine,” Biden said, urging vaccinations.