Twenty-six fire companies were shuttered in New York City Saturday, infuriating municipal officials at the show of defiance against the vaccine deadline late Friday afternoon.

Under pressure, almost 3,000 fire fighters were vaccinated in the last few days before the deadline, with Mayor Bill de Blasio expressing satisfaction that the mandate was having its intended effect, but at least 4,000 firefighters out of the total of around 17,000 have yet to be vaccinated.

According to union officials, around 70 percent of New York’s firefighters have contracted coronavirus in the past, giving them strong natural immunity that numerous studies have shown to be equal or even superior to that conferred by vaccination. FDNY-Fire Officers Association President Jim McCarthy added that the previous system of testing unvaccinated members for COVID had been working well. But although union leaders had been hopeful that the mayor would be open to negotiation regarding the remaining vaccine hold-outs, de Blasio remained insistent to the last that the mandate, and the deadline, were not going to change.

By Monday, the number of fire units out of service was down to 18 out of the 350 citywide; furthermore, 2,300 firefighters called in sick, double the usual number, prompting Fire Commissioner Daniel Nigro to accuse the absentees of staging a sick-out and engaging in “irresponsible” behavior that “creates a danger for New Yorkers.”

Responding to the sweeping accusation, the FDNY-Firefighters Association pointed out that it was entirely possible that such a large number of firefighters truly were feeling under the weather; after all, several thousand NY firefighters received vaccine shots over the weekend, and the side effects are well-known.

“We take great exception to the assertions that New York City firefighters, allegedly in the thousands, are faking medical leave because of the mandate,” International Association of Firefighters President Edward Kelly said. In fact, around half of those on sick leave have been vaccinated. But Fire Commissioner Nigro insisted that, “We know that’s related to protests against the mandate. It’s obvious … Irresponsible bogus sick leave by some of our members is creating a danger for New Yorkers and their fellow firefighters. They need to return to work or risk the consequences of their actions.”

He added, “We will use all means at our disposal, including mandatory overtime, mutual aid from other EMS providers, and significant changes to the schedules of our members. We will ensure the continuity of operations and safety of all those we have sworn oaths to serve.”

His stance was mirrored by that of Mayor de Blasio, who said, “The folks who are out sick and really aren’t sick – the folks who are faking it – are doing an immense disservice to the people of this city and to their fellow members of service. We will make sure there are consequences for that.”

He then threatened legal action if it appeared that there had been any violations of the Taylor Law, noting that, “If the union coordinates – in any way – a job action, that is a violation … [and the city will] go to court immediately … We’re watching every single thing they say and do, every email, every tweet, we are watching everything. If we see a violation of the Taylor Law, we will be in court immediately.”

At a briefing on Friday, Andrew Ansbro, president of the Uniformed Firefighters Association, warned that New York City should prepare to witness an “inevitable disaster by design” if the mandate was enforced. Certainly the FDNY was ready to deal with absences and it has already taken a number of steps to counter them, including sending requests for help to volunteer firefighters from Long Island and upstate.

Asked to explain his insistence that service had not been disrupted, Commissioner Nigro Monday described how scheduled training and maintenance had been canceled, allowing all available companies to be available at once. “Response time has been very strong,” he said.

However, sources within the FDNY noted that they had been ordered to work “straight tours” starting nine a.m. on Saturday, meaning that no shift exchanges between members were permitted and that overtime work would be scheduled in to ensure adequate staffing.

“They’re forcing us to work overtime,” one firefighter said. “That means we’ll lose another ten percent who get injured or sick from 80-hour work weeks.”

All vacations set to start Monday or later have been canceled, and anyone who wants to take their accrued comp time has to file for retirement to avoid being suspended, sources said.

Whether the FDNY can continue to operate effectively on such a footing is an open question. At a media availability on Monday, Mayor de Blasio insisted that “redundancies are built in” to the Fire Department, allowing it to cope with the absence of thousands of workers at a time.

At his side was Commissioner Nigro, telling reporters that, “Once members come to their senses and stop using medical leave improperly, they can help out not only the citizens of the city but their brothers and sisters who are staffing these units.” He added that, “The biggest consequence here for each individual [calling in sick] is their moral consequence, but the department is not without tools to look into discipline for these members.”

“When City workers such as those who are choosing not to show up to work, even though they’re not sick, when they do that, they start to lose public support,” said de Blasio. “They start to get the public, in fact, angry that people are paying taxes, but not getting the service they deserve…

“There’s a certain point where responsible, decent people who say they believe in American values need to recognize there’s been due process, democracy has happened,” he added. “The people spoke.”