NEW YORK (NYTIMES) - Hundreds of firefighters called in sick in what appeared to be an organised protest. Sanitation workers were playing catch up, after garbage collection lagged last week.

But for the most part, New York City's vast municipal workforce returned to work as usual on Monday (Nov 1), with more than a few sore arms and new vaccination cards, as the city's coronavirus vaccine mandate for its employees went into effect, officials said.

"We're not seeing disruptions to any city services," Mayor Bill de Blasio said on Monday morning.

Across all city agencies, Mr de Blasio said, about 9,000 municipal employees have been placed on unpaid leave - all eligible to return to work as soon as they get a first dose.

Another 12,000 city workers had yet to get their first dose of a Covid-19 vaccine, but had applied for a religious or medical exemption. They are allowed to continue working while the city evaluates their requests. The city has over 370,000 people on its payroll.

In the 12 days from when the mandate was first announced and Monday's deadline, the vaccination rate shot up at many city agencies.

At the city's Emergency Medical Service, which operates ambulances, the vaccination rate jumped to 87 per cent from 61 per cent. The Sanitation Department's vaccination rate jumped 20 percentage points, to 82 per cent from 62 per cent.

The adult vaccination rate across New York City is at 86 per cent.

Still, not everyone agreed with the mayor's rosy assessment that there had been no disruptions in service.

Representative Nicole Malliotakis, a Republican who represents Staten Island and part of southern Brooklyn, said that over the weekend and into Monday, multiple fire engine or ladder companies were taken out of service in her district because of staff shortages. At a firehouse in the Bath Beach neighbourhood of Brooklyn, a team of unvaccinated firefighters showed up to work, but were sent home, the firefighters union said.

"No matter what shell game the mayor is playing, the reality is these firehouses are short-staffed and not operating at full capacity, and it's putting the public at risk," said Ms Malliotakis, an opponent of the mandate.

Some public health experts, on the other hand, said the mandate did not come soon enough.

"This helped move the needle a lot for some city agencies," said Dr Denis Nash, a professor of epidemiology at the CUNY School of Public Health, adding that vaccine mandates "tend to work and have a big effect on increasing vaccine uptake".

But he wondered why the mayor had waited so long: "I personally think it should have happened a while ago."

Monday's deadline applied to all municipal workers, ranging from police officers to parks employees. It was the latest vaccine mandate to be imposed by the city or state that does not allow virus testing as an alternative.

Earlier mandates - which went into effect about a month ago - required health care workers and educators to get vaccinated. In both sectors, thousands of workers got vaccinated in the days just before the mandate deadline.

Since Monday's deadline for about 160,000 city workers was first announced on Oct 20, more than 22,400 city employees have got their first dose. Still, union leaders said that if the city had given workers more time, there would have been even more compliance.

Mr Gregory Floyd, president of Teamsters Local 237, which represents more than 18,000 municipal workers in New York City, said the time frame was too short to allow some people to book a doctor's appointment to discuss the vaccine.

"A lot of people want to speak to their doctors," Mr Floyd said, noting that many people who remained unvaccinated were anxious about the vaccine and needed reassurance. "Another week would have been really helpful."

More than 3,000 city employees waited until this past weekend to get a first dose, and still others said they had all but made up their mind and would get the shot in the coming days.

Mr Kem Farmer, a paramedic from the Bronx, attended an anti-mandate rally near Gracie Mansion on Friday, when he was considering retiring after 33 years as an emergency medical technician instead of submitting to the mandate.

But on Monday, Mr Farmer, 62, said his plan had run into resistance at home.

"My wife is pressing me to get the shot," he said. With Monday and Tuesday as scheduled days off, he has until Wednesday to return to work with proof of vaccination.

"I'm really fighting, and I'm the last holdout in my family, but it looks like I'm going to get it," Mr Farmer said.

Some of the most visible resistance to the mandate in recent days appears to have come from the Fire Department, with its close-knit, communal culture. Over the past week, more than twice as many firefighters as expected have been taking medical leave, in what the fire commissioner has described as a "protest" against the mandate.

The president of the union representing firefighters has said there was no organised sickout and that many of those taking sick days were doing so to cope with the side effects from their first dose of a coronavirus vaccine.

The majority of those taking medical leave are unvaccinated, fire commissioner Daniel Nigro, said.

On Monday, Mr Nigro implored these firefighters to "come to their senses" and return to work.

As a result of the high number of sick calls, about 18 of the department's 350 units are out of service, Mr Nigro said. But he said that was not an unusually high number, as that many units could be out of service because of training or maintenance on any given day.

Mr de Blasio said that response times for emergencies remained normal.

Though city agencies reported little strain on Monday, worker shortages could emerge in the coming weeks. About 12,000 city workers - roughly half of whom work for the Police Department - have applied for religious or medical exemptions. Pending a decision, they are allowed to keep working, so long as they provide a weekly negative Covid-19 test.

The Equal Employment Opportunity officer at each agency is tasked with making a decision about each exemption. The guidelines are likely to be strict, city officials have said.

For a permanent medical exemption, a severe allergy to the vaccine or one of its components is one of the few qualifying criteria, according to a city FAQ on the vaccine mandate.

For temporary medical exemptions, reasons include: a Covid-19 infection within the past two weeks; recent treatment with monoclonal antibodies; stem cell or other treatment that suppresses the immune system; or heart inflammation such as myocarditis.

For religious exemptions, city guidelines state that a "sincerely held religious, moral or ethical belief may be a basis for a religious accommodation", but in practice criteria are expected to be very narrow.

An employee who objects, for example, to the use of fetal cell lines in vaccine development or production may be asked to show they have refused other vaccines or medications on the same grounds.

No major religion has barred its faithful from taking the Covid-19 vaccine.

In September, the city agreed in an arbitration with the teachers union to consider religious exemptions only for staff members who belonged to an organised religion with a known objection to vaccination, such as Christian Science, supported by a note from clergy. That may serve as a guide for these judgements.

The Department of Education said on Monday that less than 1 per cent of its 150,000-member workforce had been granted exemptions - 1,100 medical exemptions, of which 670 were short term, and 150 religious exemptions.

"My understanding is there've been very few, if any cases, that have met the standard that the arbitrator set for the religious side," Mr de Blasio said Sept. 24.

The city says it will rule on all cases and appeals by Thanksgiving.