Image source, Getty Images

A standoff in Chicago, where the head of the city's largest police union is urging officers to defy a vaccine mandate, is the latest battle line being drawn in a national battle over Covid-19 jabs.

Chicago, a city of nearly three million people, has seen more than 1,600 sexual assaults, nearly 3,000 shootings and 649 murders this year – a 14% increase over last.

Just as violent crimes have risen, though, thousands of the city's police force may not show up to work.

Officers are weighing whether to resist a mayoral mandate requiring all public employees to report their vaccine status. City employees must now show proof of vaccination or submit to bi-weekly testing, unless approved for a religious or medical exemption. By the end of this year, all employees must be vaccinated.

Nearly one-third of Chicago's almost 13,000-member police department have so far refused to register their vaccination status, putting them on track for dismissal.

Twenty-one have been officially removed from active duty so far, but some officials have warned that the mandate could leave Chicago's police force dangerously depleted.

During a CNN town hall on Thursday night, President Joe Biden said US emergency responders who defy vaccine mandates should be fired.

Chicago is not alone in facing this problem. Police departments across the US have been stymied in their efforts to coax officers into getting vaccinated against Covid-19 – now the leading cause of death for police in the US, according to the Officer Down Memorial Page, a non-profit that tracks police officer deaths.

In the decade before the Covid-19 pandemic, an average of 166 US police officers died in the line of duty each year, according to the non-profit. Last year, 374 officers died – 245 of them due to Covid-19, more than any other cause combined.

"This virus is no different than the gunfire we take as cops," Chicago police superintendent David Brown said on Tuesday. "I will do everything I can and I will say anything I need to in order to convince officers to do everything they can to save their lives."

Image source, Getty ImagesImage caption, A young Chicago White Sox baseball fan get jabbed at a game

Yet vaccination rates among officers have generally lagged behind the general public.

"It's hard to understand," said Art Acevedo, who has served as chief of police in Miami, Houston and Austin, of vaccine hesitancy among police. "You'd think we'd be closer to 100% vaccination."

Mr Acevedo said he has urged reluctant officers to use their training and "look at the data".

"Every living president on both sides of the aisle has been vaccinated," he said. "In my business, we call that a clue."

Mr Acevedo attributed the resistance to a mistrust in government. Others have expressed irritation with what they see as government overreach, as well as scepticism in the vaccines' safety.

Image source, Getty ImagesImage caption, Police union boss John Catanzara has called on cops not to get jabbed

In Chicago, the head of the city's largest police union John Catanzara has called on its some 11,000 members to defy the city's requirement to report their vaccination status.

"It is the city's clear attempt to force officers to 'Chicken Little, the sky is falling' into compliance," he said last week. "Do not fall for it. Hold the line."

Mr Catanzara, who did not respond to the BBC's request for comment, has compared the mandate to "Nazi Germany" and has suggested the vaccine requirements are an illegal violation of privacy.

Image source, Getty Images

A judge last week granted the city's request for a temporary order barring Mr Catanzara from making any public comments that encourage members of his union to resist the order. However, he has continued to post videos to the union's public YouTube channel, in apparent defiance of the order.

According to Mr Catanzara, as many as 50% of Chicago's 13,000 officers would take unpaid leave rather than report their vaccine status – threatening to bring a public safety crisis to America's third-largest city.

Police resistance to vaccine mandates has been seen in at least a handful of other other cities across the US.

Los Angeles Sheriff Alex Villaneuva, who oversees the largest sheriff's department in the country, has said he will not enforce the county's vaccine requirements on his staff. Mike Solan, president of Seattle's rank and file police union, described the city's Covid-19 mandate as a "political betrayal", and said this week that up to 350 of his officers could be out of a job.

Image source, Getty ImagesImage caption, Mayor Lori Lightfoot

And in Massachusetts, the state police union is suing the governor over vaccine requirements.

In Chicago, some say the divide between police and politicians has been widened by the mayor, Lori Lightfoot, a Democrat, whose 2019 campaign was animated by promises to reform the city's force.

Police feel "vilified" by city authorities, said Raymond Lopez, a city council representative. "There's a general sense that our officers are not appreciated in the city they seek to serve and protect. Morale is low among the ranks."

Ms Lightfoot – who was criticised this month for breaking mask rules when she was photographed bare-faced at a Chicago basketball game – has held firm to her vaccine mandate.

She has accused Mr Catanzara of trying to "induce an insurrection".

And she has dismissed concerns of widespread police shortages, insisting there has been no disruption to the force so far.

Asked about the risk at a news conference, she said on Monday: "I don't engage in a lot of hypotheticals."

The number of police who have continued to say "no" after being given opportunities to comply with the reporting requirement "is very small", she said.

Still, other city officials fear the mandate will ignite a public safety crisis.

Last week, two city council representatives, Marty Quinn and Matt O'Shea, wrote a letter to Ms Lightfoot asking for the mandate to be delayed, citing "a dwindling police force and rising incidents of crime and violence".

Mr Quinn, who is vaccinated, told the BBC that a potential shortage of police is overwhelmingly the primary concern of his constituents.

Image source, Getty ImagesImage caption, Police cadets are sworn in on 20 October in Chicago

"Since last week, my phones have been burning up about what's going on," he said. "What I'm hearing loud and clear is we have to make sure that every single officer that's capable of being on the job, is on the job."

Even before the mandate, Chicagoans had been left with a pared-down police force due, in part, to record levels of retirement and budget cuts which eliminated 614 vacant positions in the department this year.

"We can ill-afford to lose any more police," said Mr Quinn.

"This is not about the mandate, it's not about Mayor Lightfoot and John Catanzara. It's about public safety".

Media caption, Watch: The showdown over Covid-19 mandates

The need for police is now at odds with another need of public safety: vaccinated frontline workers.

Their resistance to vaccine mandates reflects a broader American trend, said Chief Acevedo. "Police officers don't grow in petri dishes, they come from society."

But while battles over vaccines have broken out across professions, police officers and other frontline workers pose a particular threat.

"The issue here is when you have interactions with police officers, it's unpredictable," said Dr Abraar Karan, an infectious disease expert at Stanford University. Like a doctor, EMT or nurse, police officers have to interact with "everyone", including the elderly and immunocompromised – all of whom could be put at risk.

Indeed for some, a meeting with an unvaccinated officer or other first responder could be deadly.

"Not having police, especially in areas with high crime, will be a huge cost to citizens there," he said. "But we know that vaccines are safe… I think the risk to others is something we need to consider more seriously."

Additional reporting by Anamaria Silic