New York, New York - All New York City municipal workers – including police officers, firefighters, and teachers – will have to get vaccinated or submit to weekly coronavirus tests under a new mandate Mayor Bill de Blasio unveiled Monday.

The requirement, which will cover roughly 300,000 city workers, is set to take effect September 13, the first day of the school year. Failing to comply is likely to spell serious consequences.

If city workers who opt against vaccines refuse to wear masks indoors, they won’t be allowed to come to the job and won’t be paid, de Blasio and his Labor Commissioner Renee Campion said.

"We’re just not going to tolerate unvaccinated city employees doing the wrong thing," de Blasio said Monday at his morning press briefing. "Let’s be blunt: If you’re a city employee and you’re unvaccinated, you must wear a mask indoors at work. We will not tolerate any decision to do otherwise because this is about protecting people’s health and well-being."

Unvaccinated workers not wearing masks, he added, would be "removed" from their workplace.

"It will be a job requirement. We will expect employees to comply," Campion added. "If employees refuse to comply, they just can’t be at work and, in fact, they will not be paid."

Campion added that the new requirements will vary by agency, but didn’t offer much detail on how that would work. She and de Blasio noted that the city has discussed the move with municipal labor unions and that the conversations are ongoing.

The announcement drew an almost immediate public pushback from the largest municipal workers union.

Henry Garrido, executive director of DC 37, issued a written statement during de Blasio’s news conference saying that for the city to move forward with the plan, it must first sit down to negotiate.

"If City Hall intends to test our members weekly, they must first meet us at the table to bargain," he said. "While we encourage everyone to get vaccinated and support measures to ensure our members’ health and well-being, weekly testing is clearly subject to mandatory bargaining. New York City is a union town and that cannot be ignored."

Another powerful union, the United Teachers Federation, offered a more supportive response, suggesting that the new rule is a fair one.

"Vaccination and testing have helped keep schools among the safest places in the city," UFT spokeswoman Alison Gendar said. "This approach puts the emphasis on vaccination but still allows for personal choice and provides additional safeguards through regular testing. There are still many things to do before we are prepared to safely open our schools in September."

Last week, de Blasio ordered all public hospital and health workers in the city to either get vaccinated or undergo weekly tests starting August 2.

Aside from the new September 13 vaccine deadline, Health Commissioner Dave Chokshi also announced Monday that a similar mandate would be applied to workers in senior centers and foster care shelters sooner, starting August 16.

The mayor’s increasingly aggressive push for more vaccinations comes as the city is seeing a troubling uptick in Covid-19 infections driven by the highly contagious delta variant. On Monday, the city’s Covid-19 positivity rate stood at 2.35% after hovering below 1% for weeks.

Meanwhile, more than 40% of the city’s population remains unvaccinated, according to Health Department data. Some categories of municipal employees have even lower vaccination rates. The New York Police Department said last week that it has only administered shots to about 43% of its officers, though the overall inoculation rate is likely higher because that number does not include cops who’ve gotten vaccinated on their own time, outside the intra-department vaccination drives.

According to Chokshi and de Blasio, 71% of adults in the city have received at least one vaccine dose so far.

As part of a new vaccination push, the city will launch a mobile phone app – New York City COVID Safe – to track vaccinations and testing. The launch is scheduled for August 2.