Biden urges boosters amid omicron surge; nation's population slows to record low; Fauci OKs vaccinated family gatherings: COVID-19 updates.

The nation's population growth has dipped to its lowest rate ever as a result of the ravages of the COVID-19 pandemic, according to figures released Tuesday by the Census Bureau.

Coronavirus curtailed immigration, delayed pregnancies and killed over 800,000 U.S. residents. The nation grew by only 0.1%: Specifically, an additional 392,665 people from July 2020 to July 2021.

It's the first time since 1937 that the U.S. population grew by fewer than 1 million people and the lowest growth since at least 1900, when the Census Bureau began population estimates.

Population growth has been slowing for years due to lower birth rates, decreasing international migration and rising mortality rates from an aging population.

"Now, with the impact of the COVID-19 pandemic, this combination has resulted in an historically slow pace of growth," said Kristie Wilder, a Census demographer.

Also in the news Tuesday:

►In Chicago, anyone 5 years or older must show proof of vaccination starting Jan. 3 to dine indoors, use gyms, or visit entertainment venues where food or drink are being served, Mayor Lori Lightfoot announced Tuesday.

►Minnesota Gov. Tim Walz, his wife, Gwen, and their 9th grade son, Gus, have all tested positive. Gov. Walz said all were vaccinated and that he and his wife have no symptoms while his son has "sniffles."

►Tedros Adhanom Ghebreyesus, director-general of the U.N., urged people everywhere to rethink holiday events. "It's better to cancel now and celebrate later, (rather) than to celebrate now and grieve later," Tedros said.

►Massachusetts Gov. Charlie Baker announced Tuesday he will activate up to 500 members of the National Guard to support understaffed hospitals facing a surge of COVID-19 patients and to bolster non-emergency medical transportation needs.

►Britain will spend $1.3 billion to help the hospitality industry survive the onslaught of the omicron variant, bowing to days of pressure from pubs, restaurants and other businesses that have seen their income plunge amid public health warnings.

Today's numbers: The U.S. has recorded more than 51 million confirmed COVID-19 cases and more than 807,800 deaths, according to Johns Hopkins University data. Global totals: More than 275.3 million cases and 5.3 million deaths. More than 204 million Americans - 61.5% of the population - are fully vaccinated, according to the CDC.

What we're reading: As COVID-19 rates spike in a time of omicron, here's what you need know to stay safe during the holidays.

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Biden urges vaccines, masks amid holiday omicron surge

President Joe Biden told Americans Tuesday that COVID-19 vaccines and third shot boosters provide strong protection against the omicron variant of the coronavirus. Vaccines, medical supplies and knowledge about COVID-19 have put the country in a much better place now than in March 2020, Biden said.

"We're prepared today for what's coming. In March 2020 we were not ready," Biden said.

The president recognized that Americans have concerns of visiting loved ones for the holidays, given the rapid spread of omicron. Biden stressed booster shots and vaccines for children, including for 5-11 year-olds.

"People with booster shots are highly protected. Join them," he said.

The president outlined plans to roll out thousands of additional COVID-19 testing sites, and a federal government purchase of half a billion at-home rapid tests. Americans will not be able to request the at-home tests online until January, meaning they can't access the kits before millions are expected to travel for Christmas.

White House press secretary Jen Psaki said the federal government is still working through details of the program, including whether some groups would be prioritized.

The 500 million tests are in addition to 50 million tests the Biden administration began distributing this month to community health centers.

The Biden administration hopes to make at-home tests an insured expense and possibly expand access to free tests for the uninsured.

"It's a lot better than it was and we're taking steps to make it easier to get tested and tested for free," the president said.

NYC mayor-elect delays inauguration; New Year's Eve celebration in doubt

New York Mayor-elect Eric Adams postponed his inauguration ceremony, scheduled for Jan. 1 indoors at Brooklyn's Kings Theatre. Adams, who will still become mayor that day, said the ceremony would be rescheduled for a later date "to prioritize" the health of attendees, staff and reporters.

"It is clear that our city is facing a formidable opponent in the omicron variant of COVID-19, and that the spike in cases presents a serious risk to public health," Adams said.

Mayor Bill de Blasio said he hopes to make a decision by Christmas on whether the iconic Times Square New Year's Eve celebration will take place.

Fauci: Family holiday gatherings OK for vaccinated Americans despite infection surge

Americans preparing to spend time with family and friends this holiday season don't need to cancel plans, despite the latest infections surge, if they are vaccinated and boosted, Dr. Anthony Fauci said Tuesday.

Fauci, making the rounds of the morning news shows, acknowledged the alarming surge driven by the omicron variant. Omicron is now the dominant version of the coronavirus in the U.S., accounting for 73% of new infections last week.

"If you don't have the availability of the test and you are fully vaccinated and boosted, you should feel comfortable having a holiday meal or gathering with family members who are also vaccinated and boosted," he said on NBC's "Today."

Speaking on CNN's "New Day," Fauci said hospitalization numbers are more important than infection numbers.

"If we have a larger number of people getting infected, but the degree of severity is very, very low, that would be very important," Fauci said. "If you just count the numbers of infections, you may get a misrepresentation as to what is actually going on."

Schools bracing for more issues as omicron rolls in

Across the country, school districts and families are stumbling toward the finish line of a punishing semester.

At some points, nearly all schools appeared back to normal with daily, in-person instruction. COVID-19 exposures sent kids and staff home to quarantine. Teachers battled student misbehavior, from low-level defiance to more fights, threats and gun violence. Staffing shortages shot up. Parents waged their own arguments over race, public health and other issues.

And now, omicron. Schools and districts are shuttering and some are preparing to return to virtual instruction.

"We're going to see a return, basically, to a good portion of how things looked last year," said Dan Domenech, executive director of the School Superintendents Association. "The schools want to stay open. But it's a logistical nightmare." Read more here.

- Erin Richards, USA TODAY

Cleveland physician: Too early to assume omicron is less severe

Dr. Laolu Fayanju, regional medical director at Oak Street Health in Cleveland, says it's too soon to confirm the growing narrative that the omicron variant is more infectious but less dangerous than other forms of the coronavirus.

Fayanju cited a recent study from researchers at the Imperial College of London that looked at data from people who tested positive in the U.K. between Nov. 29 and Dec. 11 - and found no evidence the omicron variant is milder than delta. Even if the variant causes slightly milder symptoms, but is much easier to spread, and it has the capability of partially evading defenses in the immunized, "we are not out of the woods," he said.

"The description of the omicron variant being mild as compared to other variants is not merely a myth, but a dangerous and potentially disastrous framing that we need to abandon," Fayanju said.

Tips for safely spending the holidays with friends and family

As COVID-19 cases surge, Americans are wondering how to approach the holidays and safely travel and gather with friends and family. The pace of new cases in the U.S. is up 41% compared to a month ago, according to a USA TODAY analysis of Johns Hopkins data. For much of December, cases appeared to hover around 120,000 but have recently jumped to 140,000 a day.

Still, people who are fully vaccinated do not need to quarantine after contact with someone who had COVID-19 unless they develop symptoms, the Centers for Disease Control and Prevention says. However, they should still get tested five to seven days after their exposure and wear a mask in indoor public settings for 14 days following exposure or until they get a negative test result. For more tips, read more here.

- Adrianna Rodriguez

California hoping to avoid tight restrictions, hospital crisis

California is poised for a surge in new coronavirus infections sweeping the nation, but experts are hoping the state can avoid another wave of crippling restrictions. California has fared far better than many other states so far, with areas in the Midwest and Northeast seeing the biggest surge in cases and hospitalizations amid frigid temperatures that have kept people indoors. And the state ranks near the top in percentage of vaccinated residents. Thus the nation's most populous state could avoid the worst scenario - spikes in hospitalizations and deaths.

"It's a highly transmissible respiratory virus and people are going to get it. And they are going to get it every winter," said Dr. Monica Gandhi, a professor of infectious diseases at the University of California, San Francisco. "We have to go toward measuring our true success with a disease, which is how we're doing with hospitalizations."

Not all the omicron news is bad

Although details about the omicron variant are still sketchy, a picture is starting to emerge - and it's not all bad news. So far, it's clear that omicron is highly contagious - roughly twice as contagious as delta and four times more than the original virus. Experts worry that even if it's less virulent, which isn't yet clear, it could still cause enough hospitalizations to overwhelm health care systems here and abroad.

But this is not 2020. Back then, only a handful of people on earth had been exposed to the SARS-CoV-2 virus that causes COVID-19. Everyone's immune system was unprepared. And now we have vaccines.

"I think we should reassure people that if they've been vaccinated with two doses or naturally infected, they're likely protected against serious illness," said Dr. Paul Offit, a pediatric infectious disease expert and director of the Vaccine Education Center at Children's Hospital of Philadelphia.

- Karen Weintraub, USA TODAY

Royal Caribbean ship returns to port to remove infected passenger

A Royal Caribbean International ship, Odyssey of the Seas, briefly returned to port to disembark a passenger with COVID-19 one day after departing from Fort Lauderdale,

The cruise had set out Saturday on an eight-night itinerary from Florida before returning Sunday. The passenger and his family disembarked and there were "no additional close contacts," said Lyan Sierra-Caro, spokesperson for Royal Caribbean.

"The guest, who was symptomatic prior to boarding but did not notify us, reported to the medical center and subsequently tested positive for COVID-19," Sierra-Caro told USA TODAY. "He and his close contacts were quarantined (aboard the ship) and disembarked in Ft. Lauderdale to return home."

- Morgan Hines, USA TODAY

Contributing: The Associated Press