NEW YORK (CBSNewYork) — New York City workers face an ultimatum Friday: Get vaccinated or be placed on unpaid leave.

Thousands of them protested the vaccine mandate Thursday in front of the mayor’s home.

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FDNY unions hosted the demonstration outside Gracie Mansion. So far, 71% of FDNY members are vaccinated, along with 78% of the NYPD, and 65% of the Department of Sanitation.

With the clock ticking down to Friday’s 5 p.m. deadline, many called the rally their “last stand.”

“This is really an absolutely unnecessary threat to the lives of New Yorkers,” said Andrew Ansbro, president of the Uniformed Fire Fighters Association. “There is no crisis. Right now, 8% of New York City firefighters are out with fire-related injuries, and one-sixteenth of that number is out with COVID.”

“We worked through this pandemic over a year. We worked!” Firefighter Jackie Michelle Martinez said.

Martinez is among the many essential workers who packed the street to send a clear message to the mayor.

“We are not anti-vaccine. We are here because we are pro-choice,” Martinez said.

“I think its extraordinarily shortsighted to take people he just had a ticker-tape parade for a few short months ago and cast them aside,” retired firefighter Kieran Burke said.

WATCH: CBS2’s Jenna DeAngelis Reports From Scene Of Rally 

The city says it’s ready to show the door to 3,500 FDNY members if they don’t get the shot before Friday. A high-ranking FDNY source told CBS2 as many as 20% of fire companies could close, and the department’s ambulance fleet may be impacted as well.

Those attending the rally said if the mayor doesn’t budge on his mandate, it could mean lives are lost.

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“No other way to do this,” Ansbro said. “We currently have a staffing shortage as it is.”

“We got nine days, nine days, to decide. That’s crazy. Our members deserve better. We demand the de Blasio administration treat us better. We want to bargain all these implementations,” Uniformed Fire Officers Association President Jim McCarthy added.

Mayor Bill de Blasio defended the mandate Thursday, saying the FDNY commissioner has a contingency plan.

“Mandatory overtime, scheduling changes, there’s other options they can turn to to address the situation,” he said. “We will be ready. If folks show up who are not vaccinated, their supervisors will address that.”

McCarthy argued 70% of members have already been infected and have natural immunity, so they don’t need to be vaccinated. However, the mayor and city’s health commissioner said that’s not good enough.

“The strength and the duration of that immunity remains unknown,” said Dr. Dave Chokshi.

COVID VACCINE

As the window to vaccinate closes, there’s growing concern about gaps in services in other city departments.

A state Supreme Court judge denied the Police Benevolent Association’s lawsuit to halt the mandate, upholding that officers must have their shots. The union president said the ruling “sets the city up for a real crisis,” adding, New Yorkers should blame the mayor and police commissioner.

The FDNY unions insist they have been pro-vaccine the entire time, but they’re also pro-choice. Ansbro said they’ve seen as many retirement requests in the last two days as they typically see in a month.

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CBS2’s Jenna DeAngelis and Ali Bauman contributed to this report.

John Dias