NEW YORK (PIX11) — A COVID vaccine mandate for all New York City private businesses and their employees took effect Monday as omicron cases continued to surge. The city’s latest vaccine mandate, announced by outgoing Mayor Bill de Blasio in early December, says all companies in the city must require their workers to show proof of vaccination.

Starting Monday, in-person workers have to provide proof they have received at least one dose of the vaccine. They will not be allowed to get out of the requirement by agreeing to regular COVID testing instead. Businesses will be required to verify and keep a record of each employee’s proof of vaccination.

The mandate is, so far, the most sweeping vaccine sanction of any state or large city in the country. It applies to roughly 184,000 businesses not covered by previous vaccine mandates, ranging from multinational corporations to mom-and-pop businesses in the city of 8.8 million people, according to a spokesperson for the mayor. The city’s private-sector workforce is 3.7 million.

The new rules cover private places where work is performed in the presence of another worker or a member of the public. That includes stores, shared workspaces, and taxis. Businesses that do not comply face fines starting at $1,000, though the mayor has said penalties would be a last resort.

De Blasio said the moves were aimed at staving off a spike of infections amid holiday gatherings and the cold weather, which drives more people indoors, where the virus can spread more easily. It takes effect just days before he leaves office and is succeeded by Mayor-elect Eric Adams.

An Adams spokesperson said in a statement, “The Mayor-elect will evaluate this mandate and other COVID strategies when he is in office and make determinations based on science, efficacy, and the advice of health professionals.”

Also on Monday, the city’s Key to NYC Pass program gets a bit stricter for young New Yorkers. Now, anyone 12 or older who wants to dine indoors at a restaurant, go to a gym or see a show in New York City will have to produce proof of having received two shots of the vaccine, up from the former requirement of one dose. And now children 5 to 11 will have to show proof of at least one shot.

The Associated Press contributed to this report.