(CNN)The United States is likely in for a hard winter as the Omicron variant of Covid-19 spreads rapidly, Dr. Anthony Fauci says, straining a health care system already battered by the Delta variant.
"It's going to take over," Fauci, the nation's top infectious disease expert, said of the Omicron variant on CNN's "State of the Union" Sunday, urging Americans to get vaccinated and get their booster shots. "And be prudent in everything else you do: When you travel in your indoor settings that are congregated, wear a mask."
"We can't walk away from that Jake, we can't," he told CNN's Jake Tapper. "Because with Omicron, that we're dealing with, it is going to be a tough few weeks to months as we get deeper into the winter."
According to the World Health Organization, Omicron cases are doubling every 1.5 to 3 days with documented spread. And in the US, it's expected to become the "dominant strain" in the coming weeks, the director of the US Centers for Disease Control and Prevention said Friday.
The US is now facing a resurgent coronavirus as the pandemic marches into its third year: The country was averaging 126,967 new cases per day as of Saturday, according to data from Johns Hopkins University -- up from an average of just over 70,000 new cases per day at the beginning of November.
"This Omicron variant is extraordinarily contagious. It's as contagious as measles, and that's about the most contagious virus that we've seen," CNN medical analyst Jonathan Reiner said Saturday, warning there was a "tsunami" coming for unvaccinated Americans.
Scientists say it's still too early to tell whether Omicron causes a milder form of Covid-19 disease. But regardless, it will put pressure on the health care system, Reiner said.
"Why would you go into that kind of battle completely unarmed?" he said. "Our vaccines will protect you, particularly if you are triple vaxed. People who are unvaxed should start the process now. Go ahead and go to your pharmacy and get vaccinated."
Reiner, a professor of medicine and surgery at George Washington University School of Medicine & Health Sciences, said he believes almost everyone will be exposed to the virus -- but those who are triple vaccinated will not necessarily contract Covid-19.
"But I do not think that we need to just throw our hands up in the air and say, 'Look, we're all going to get it so let's just let it burn through the country.' If we do that, our hospitals will be swamped," he said.
Even if Omicron ends up causing less severe infection than Delta, the sheer number of infections Omicron could generate could overwhelm US hospitals, Reiner said.
More than 69,000 people are hospitalized with Covid-19 across the US and more than 20% of all ICU beds are occupied by Covid-19 patients, according to the US Department of Health and Human Services.
"We need to protect our health care system," Reiner said, "and that's why every American needs to mask up and vax up right now because our health care infrastructure is at stake right now."
'Do not wait' to get a booster, expert says
According to CDC data, about 61.4% of the total US population is fully vaccinated, and about 29.1% of those have received a booster, which health officials point to as a crucial line of defense against the Omicron variant. And yet many who are eligible for a booster shot have not gotten one.
The protection offered from two-dose mRNA vaccines -- like those by Pfizer/BioNTech and Moderna -- is "quite good particularly against severe disease," Fauci said Sunday.
"But when you get to Omicron, the protection significantly goes down," he said. "But the good news is when you boost someone, it goes right back up."
Dr. Francis Collins, the outgoing director of the National Institutes of Health, told CBS' "Face the Nation" Sunday people should not wait to get boosted.
"A big message for today is, if you've had vaccines and a booster, you're very well-protected against Omicron causing you severe disease," he said. "So anybody listening to this who is in that 60% of Americans who are eligible for a booster but haven't yet gotten one, this is the week to do it. Do not wait."
On Saturday, New York state broke its record for the highest single-day Covid-19 case count since the beginning of the pandemic for a second consecutive day. Gov. Kathy Hochul's office reported 21,908 positive Covid-19 cases, up from 21,027 on Friday.
Covid-19 hospitalizations across the state remained relatively low at 3,909, compared to a peak of 18,825 Covid-19 related hospitalizations on April 13, 2020, according to available data.
"This is not like the beginning of the pandemic," Hochul said in a statement Saturday. "We are prepared for the winter surge because we have the tools at our disposal."
In New York City, Covid-19 cases more than doubled from the beginning of the week on December 13 to Saturday. But Covid-19 hospitalizations remained around the same throughout the week, with a slight spike in hospitalizations reported Saturday, according to data released by Mayor Bill de Blasio's office. In response, de Blasio announced the city would start distributing half a million at-home rapid Covid-19 tests for free through community organizations.
The surge has already affected the city's entertainment industry, canceling a number of Broadway shows in recent days -- just months after Broadway began welcoming audiences back after an extended pandemic hiatus.
This weekend's "Saturday Night Live" had no in-studio audience and aired mostly pre-taped segments due to the rise in Covid-19 cases.
The move followed the cancellation of some Broadway performances and the Radio City Rockettes' "Christmas Spectacular" shows for the rest of the year.
Maryland is bracing for what Gov. Larry Hogan, a Republican, on Sunday said could be the "worst surge we've seen in our hospitals throughout the entire crisis," telling "Fox News Sunday" hospitalizations are already up about 150% over the last two weeks.
California health officials said Friday they were seeing hospitalization numbers begin to trend upward, stressing the need for vaccinations and booster vaccines.
In New Jersey, "we're seeing long lines outside of our testing clinic, more demand than we've seen in many months for testing, because folks are getting sick," said Dr. Shereef Elnahal, president and CEO of University Hospital in Newark.
Hospitalizations have doubled over the last two weeks, he said, and although 46% of those hospitalized earlier this week had been vaccinated, they had not had a booster shot.
Dr. Rob Davidson, an emergency room physician in Michigan, said he's seeing a "pretty critical Delta surge right now." And while he's seeing the test positivity rate slightly decrease, Covid-19 patients are staying in the hospital for extended periods of time.
Dr. Marc Gorelick, who heads Children's Minnesota hospital, said the facility is already struggling to cope with the numbers.
"When you're on top of a surge where you're already at 90%, 95% capacity, those extra ... preventable Covid patients coming in are the thing that pushes the system to the brink. And that's what we're seeing here in Minnesota," Gorelick said Friday.
In Oregon, officials forecast a grim early 2022.
"We can expect a surge in Oregon hospitalizations by mid-January, with infections that begin sooner than that," said Dr. Peter Graven, a data scientist for Oregon Health and Science University.
"Combined with its heightened transmissibility, we expect Omicron will generate a large increase in the number of Oregonians that will become severely ill and likely need a hospital."
As hospitals continue to feel the burden of Covid-19 infections, scientists are racing to gather more information on the Omicron variant's severity.
The CDC said last week it looked at 43 cases of Omicron and most of those people had mild symptoms. Most were vaccinated, with about a third of the total group boosted.
"We've seen cases of Omicron among those who are both vaccinated and boosted, and we believe these cases are milder or asymptomatic because of vaccine protection. What we do know is we have the tools to protect ourselves against Covid-19. We have vaccines. We have boosters," CDC Director Dr. Rochelle Walensky said Friday.
Data from two weeks of South African cases appeared to indicate Omicron was milder in severity. But UK epidemiologists said last week they found no evidence Omicron is causing milder disease there -- although the Imperial College London team also said there was not much data to go on yet.
It's still too soon to assume Omicron will cause milder disease, and people needed to protect themselves with vaccines and boosters, said Dr. Francis Collins, director of the National Institutes of Health.
But it's "clear that Omicron is an extremely contagious variant, that it doubles every two to four days," Collins said Friday.
"The problem, of course, is if this is so infectious -- and we might see hundreds of thousands of cases every day, maybe even a million cases in a day from Omicron -- even if it's a little less severe, you are going to have a lot of people in the hospital and our hospitals are already really stretched with Delta, especially in the northern part of the country," Collins said.
CNN's Christina Maxouris, Artemis Moshtaghian and Laura Studley contributed to this report.
