• The mandate will go into effect on Dec. 27, Mayor Bill de Blasio said.
• The mandate applies to in-person employees who are in a workplace with other co-workers, de Blasio said during a news conference Monday.
• It doesn't give unvaccinated employees the option to get tested regularly, de Blasio said.
• New York has identified eight cases of the omicron variant as of the weekend, seven in the New York City area and one in Suffolk County on Long Island.

New York City is imposing a vaccine mandate for all private sector employers as a preemptive measure to fight a surge of Covid cases this winter, Mayor Bill de Blasio announced Monday.

The mandate covers 184,000 businesses and will go into effect on Dec. 27, and it doesn't give unvaccinated employees the option to get tested regularly, de Blasio said. They must have at least one dose by that date. The policy applies to in-person employees who are in a workplace with other co-workers, de Blasio said during a news conference Monday.

The city will publish guidelines on Dec. 15 to provide more information on implementation and enforcement, de Blasio said. The outgoing mayor said he has spoken with Mayor-elect Eric Adams about the policy.

"We've got omicron as a new factor, we've got the colder weather, which is really going to create additional challenges with the delta variant, we've got holiday gatherings," de Blasio told MSNBC earlier Monday morning. "We in New York City have decided to use a preemptive strike to really do something bold to stop the further growth of Covid and the dangers it's causing to all of us."

The New York City policy comes after the Biden administration was forced to halt implementation and enforcement of national vaccine and testing requirements for businesses with 100 or more employees to comply with a federal court order.

"The commissioner of health has the authority to issue a mandate like this to protect the public health and his authority to do that has been upheld time and again," Georgia Pestana, the city's corporation counsel, said during the news conference with de Blasio. "The trouble that the Biden administration has run into in court doesn't really apply here."

The city will also require everyone 12 and older to show proof of two vaccine doses – as opposed to one dose under the prior policy – for indoor dining, fitness, entertainment and performance venues starting Dec. 27 unless they received Johnson & Johnson's single-dose vaccine.

Children ages 5 to 11 will be required to show proof of a single vaccine dose by Dec.14 for those venues, the mayor said. They will also have to show proof of one dose for high-risk extracurricular activities such as sports, band, orchestra and dance by the same date.

De Blasio said the purpose of the vaccination requirements is to avoid the shutdowns imposed in March 2020 when Covid devastated New York City and its economy.

"We cannot let those restrictions come back, we cannot have shutdowns here in New York City, we got to keep moving forward," de Blasio during the news conference. "Vaccination works and vaccine mandates work, that's the bottom line."

New York City already has a high rate of vaccination, with 77% of residents having received at least one dose, according to city data. New York has identified eight cases of the omicron variant as of the weekend, seven in the New York City area and one in Suffolk County on Long Island.

"I'm sorry to say that you can expect community spread," de Blasio said. "We have to assume it's going to be widespread. We have to assume it's going to give us a real challenge."

"We've been to this movie before, we've been down this road before. We know what happens when we get a new variant, particularly one that's highly transmissible," De Blasio said. "We are not going back to what happened in 2020," he said.

Covid cases are increasing in New York City, with more than 1,500 new cases confirmed daily on average, according to the city's health department.

"We've seen case numbers grow in recent weeks due to delta, the devil we know," New York City Health Commissioner Dave Chokshi said at the briefing with de Blasio. "They have more than doubled since a recent low point in early November, increasing in every borough and every age group."

Public health officials are worried about a surge in Covid cases this winter from the delta variant as people gather inside to escape the winter chill. They are also concerned that the omicron variant could drive a spike in cases. The World Health Organization said last week that early data suggests omicron is more contagious than past variants, though more information is needed.

It's unclear whether omicron causes more severe disease, according to the WHO. The people who have tested positive for omicron in the U.S. so far have shown mild to moderate symptoms.

Clarification: Unvaccinated employees at private companies must show proof of one dose by Dec. 27. Everyone 12 and up must show proof of two doses by that date for indoor dining, fitness, entertainment and performance venues.