NEW YORK >> With President Joe Biden’s vaccination mandate for large companies in Supreme Court limbo, and the omicron variant filling hospitals to bursting, New York City is pioneering a new approach to pandemic management.

On Monday, Mayor Bill de Blasio’s vaccine mandate for private businesses went into effect, a requirement that his administration says is the most sweeping in the nation and among the most ambitious in the world.

Austria is instituting a mandate for its entire adult population, and France is requiring certain employees to work from home. But some of the most expansive efforts in the United States, such as a push to require vaccinations of Los Angeles schoolchildren, have run into roadblocks amid a lack of compliance.

In New York City, coronavirus vaccines were already required for public-sector employees, as well as patrons and staff at restaurants, indoor entertainment venues and gyms. Now, all other private employers in the city must verify that their on-site workers have received at least one dose of a vaccine. If employees have opted for a two-dose vaccine, they must submit proof that they have received the second dose within 45 days.

“I am 110% convinced this was the right thing to do, remains the right thing to do, particularly with the ferocity of omicron,” de Blasio said Monday, after giving a “key to the city” to music icon Patti Smith. “And I don’t know if there’s going to be another variant behind it, but I do know our best defense is to get everyone vaccinated and mandates have worked.”

This is de Blasio’s last week as mayor, and it remains unclear if his successor, Eric Adams, will keep the mandate in place, or if he will modify it in response to concerns from business owners. He has consistently refused to say, and Monday proved no different.

“The mayor-elect will make announcements on his administration’s COVID policy this week,” his spokesperson, Evan Thies, said in a text message.

Vaccines and boosters appear to largely prevent the most severe symptoms in omicron infections. But the ability of the variant to cause breakthrough infections in vaccinated people, and the havoc those infections have wrought on the city and on businesses, has made the new requirement among the least of employers’ concerns, according to Randy Peers, who runs the Brooklyn Chamber of Commerce.

“What small businesses are really focused on right now is omicron and the impacts,” Peers said. “We’ve got the holiday season, which was a bust for many small businesses, because they didn’t have the customer foot traffic they would have. We have small businesses who are losing employees to omicron, so they’re short-staffed. And these are mostly vaccinated employees.”

De Blasio promised that enforcement would be light during his final week as mayor. City officials will inspect businesses, and only business owners who flat-out refuse to cooperate with the mandate are likely to face fines, de Blasio said.

“Our inspectors will be out there energetically, but with the goal, you know, educate and correct, ideally, avoid penalties,” de Blasio said.

In New York City, well over 100,000 people have tested positive since the start of last week, more than 1% of the city’s population. Across the state, about 5,525 patients are hospitalized with COVID-19.

Transit officials on Monday said there would be some delays in subway service this week because of the rising number of Metropolitan Transportation Authority workers who have tested positive. Passengers may find themselves waiting “a minute or two longer” for the next train, said Janno Lieber, acting chair and CEO of the MTA. But de Blasio said the rapid spread of omicron “has not affected the operations of the city.”

On Friday, the state Health Department warned that there had been a “fourfold” increase in pediatric hospitalizations for the coronavirus in New York City over the course of December. Although the number is small — between Dec. 19 and Thursday, 68 children in New York City were hospitalized for COVID — health authorities said the recent increase underscored the importance of vaccinating children against the virus.

“We need to get child vaccinations up,” New York’s health commissioner, Dr. Mary Bassett, said Monday.

During his final months as mayor, de Blasio has leaned heavily on vaccine mandates and proselytized their benefits to national TV audiences. Should he run for governor next year, as expected, mandates may be a part of his statewide pitch.

The mandates appear to have helped drive the vaccination rate up in New York City. As of Monday, 80.5% of all New Yorkers had received at least one dose of a vaccine, and nearly 72% were fully vaccinated.

Public health researchers widely back the requirements. Some business owners also offered measured support Monday, including Randy Klein, owner of Whiskers Holistic Pet Care on East Ninth Street in Manhattan, where a plastic-sheeted enclosure that employees call “the fishbowl” was being reinstalled around the central cash register to help protect against the omicron variant.

Klein, who also has a Whiskers store in the Astoria neighborhood of Queens, said that all but one employee had already been vaccinated and that the last holdout recently fell in line — a “direct result of the mandate,” she said.

Klein, who opened the East Village store in 1988, said some of her customers have died of COVID and some have never fully recovered.

“I would like to see people smarten up so that we don’t have to have a mandate in the first place,” she said.

But the latest mandate has also sparked dismay among some of Klein’s peers in the business sector, given that it came at the tail end of de Blasio’s tenure and amid the staffing challenges that many businesses are facing.

Many employers across Staten Island, the city’s most politically conservative borough, are frustrated by the vaccine mandate, said Linda Baran, president and CEO of the Staten Island Chamber of Commerce.

“I got a lot of phone calls from businesses asking, ‘What are we supposed to do? Should we comply? We’re going to have a new mayor, what is the new mayor thinking?’ ” Baran said. “I think the biggest frustration here is that a lot of businesses are just having a hard time hiring and keeping employees.”

Some businesses have decided to let employees use their vacation time between now and when the next administration begins, in an effort to avoid fines, Baran said. And one of her members, who sells baked goods in Staten Island and New Jersey, is considering simply sending two employees to work out of the company’s New Jersey outfit instead.

Kathryn Wylde, CEO of the Partnership for New York City, which represents many major corporations, said businesses were grappling with an uncomfortable situation: Many of their employees who are still resistant to vaccines are people of color who may lack trust in the health care system.

Others are essential workers who have jobs that require them to appear in person. “Ironically, most of the remote workers are vaccinated,” she said.

Even as some business leaders express discomfort with the mandate, some public health researchers argue that de Blasio’s efforts have not gone far enough.

Denis Nash, a professor of epidemiology at the CUNY Graduate School of Public Health, said de Blasio should also cancel the city’s New Year’s Eve celebration in Times Square, which de Blasio said last week would be somewhat scaled back in response to the virus.

Nash argued that the event, which will still admit thousands of spectators, would attract tourists who would fraternize indoors at bars and restaurants before and after the outdoor event. They may then return home with the virus in tow, he said.

Nash called for additional efforts to stem the virus’s spread. “Maybe it’s reduced capacity at restaurants and bars, maybe it’s fewer restaurants and bars to remain open, maybe it’s testing to go to certain events,” he said.

Ronald Scott Braithwaite, a professor of medicine and population health at New York University Grossman School of Medicine, said booster requirements should be on the table, too.

“You get so much more from the booster than you get from the two doses of the vaccine,” Braithwaite said.

Michael Dorf, founder of City Winery, a restaurant and music venue with locations in New York and other cities, said the arrival of omicron has cost his business about $1 million this holiday season. The variant has bolstered the need for mandates, he said, if only because vaccinations lessen the severity of the disease.

He said his company — which employs roughly 1,000 workers, including about 400 in New York state — has even more stringent measures already in place.

“Every single human breathing person coming into the building has to be vaccinated and tested,” Dorf said. He said he planned to impose a booster requirement for all staff members and visitors starting Jan. 10.

Similarly, Rachael Moss, a ceramics instructor at Choplet Gallery and Ceramic Studio in Brooklyn’s Williamsburg neighborhood, said the gallery had been requiring its 25 employees, as well as its patrons, to be vaccinated since this summer.

Moss said she hoped the incoming mayor, Adams, would keep the mandate in place.

With a sister who is immunocompromised, she supports any mandate that will help end the pandemic.

“I don’t mind getting as many vaccines as it takes,” she said.

This article originally appeared in The New York Times.