NEW YORK (CBSNewYork)Mayor Bill de Blasio‘s COVID-19 vaccine mandate is generating major pushback from public employee unions. They are are vowing legal action and predicting dangerous staffing shortages that could impact the safety of city residents.

Most of the union leaders CBS2’s Marcia Kramer spoke to on Wednesday said they have members who simply don’t want to put the vaccine in their bodies. That includes cops, firefighters, sanitation workers, and emergency medical personnel. A shortage in each of those agencies would be felt by city residents.

And if de Blasio can’t find some way to get them to go along, agencies could be faced with a dramatic drop in city services.

“Thousands will walk off from EMS. Thousands of others will walk from fire. Thousands of police officers will walk off,” said Oren Barzilary, president of Local 2507, which represents EMTs and paramedics.

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Barzilay said he has met with dozens of angry emergency medical workers, who, for a variety of reasons, are ready to leave their jobs rather than comply with the mayor’s vaccine mandate.

And while worker shortages can affect public safety, Barzilay said a shortage of ambulances can lead to more serious consequences.

“People will die. When it comes to EMS, minutes count. When you have a life-and-death situation, where you stop breathing, and you don’t get an ambulance, there within four to six minutes, clinical death begins. There’s no time to play here with people’s lives,” Barzilay said.

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Only 50% of EMS workers are currently vaccinated. Additionally, 60% firefighters, 71% of cops, 60% of sanitation workers, and 51% of correction officers are vaccinated, officials said.

“I think certain city services are going to be affected. I really do, no matter what agency you’re talking about,” said Harry Nespoli, president of the sanitation union and head of the Municipal Labor Council.

Nespoli said the city’s unions intend to sue. They want the mayor to offer religious exemptions, a weekly testing option, and, in some cases, recognition of a theory that workers who have had COVID have immunity to the disease.

He also said that if thousands of city workers balk at taking the shot, the city could be faced with hundreds of millions, if not billions, of dollars in overtime.

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De Blasio, who is reportedly eyeing a run for higher office, is okay with shelling out more money, even though it could saddle his successor with the bill.

“Obviously, we’ll use overtime when we need to use overtime. We’ll do redeployments when we need to do redeployments. We have a variety of ways we can adjust the use of the workforce. We feel confident that even if there is some temporary dynamic of some people not being ready right away, we’re going to find our way through it,” de Blasio said.

Still, there are a lot of people who say they won’t get the shot.

James Daly, a retired FDNY three-star chief, said his three sons who work for the department are among them.

“I’m here to fight for their right to choose,” Daly said. “They were the heroes of this city and now they’re being demonized by this mayor, who’s looking to take away their paycheck.”

“I would be dishonoring God if I did take this vaccine,” EMS worker Sally Moran added.

De Blasio’s successor will have to deal with staff shortages and new overtime costs. Democratic mayoral nominee Eric Adams says it’s essential to get city workers vaccinated, but adds the city needs to work with the unions to make sure there’s a buy-in.

Republican Curtis Sliwa is against forcing city workers to choose between a shot and a job. He says they should be offered a testing option.

Marcia Kramer