After Chicago Mayor Lori Lightfoot said all city employees would "absolutely" be required to be vaccinated, the leading police union vowed to take action in court against if such mandate is announced.  

"We are 100% against mandated vaccines for our members," Chicago Fraternal Order of Police president John Catanzara, whose union represents rank-and-file police officers, said in a statement to Fox 32.

"This vaccine has no studies for long-term side effects or consequences. None," he continued in a similar statement to the Chicago Sun Times on Tuesday. "To mandate anybody to get that vaccine, without that data as a baseline, amongst other issues, is a ‘Hell, no’ for us."

Negotiations about the specifics of a vaccine mandate are ongoing with several unions, and Lightfoot has not announced when such requirement for some 33,000 city employees would take effect. 

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Lightfoot voiced support for a "vaccine mandate" for city employees when asked at an press conference Monday just hours after the FDA granted full approval to Pfizer's COVID-19 vaccine for individuals 16 years and older, moving past its emergency clearance stage. The FDA said that the companies have committed to conducting post-marketing safety studies.

"City employees are absolutely going to be required to be vaccinated," Lightfoot said, according to the Chicago Tribune. "We’re working through those discussions which have been ongoing now for a couple weeks with our colleagues in organized labor that represent city employees." 

"But we absolutely have to have a vaccine mandate," she continued. "It’s for the safety of all involved, particularly members of the public who are interacting with city employees on a daily basis. It’s important for colleagues to also feel like they have a workplace that’s safe. So a vaccine mandate from the city will come, and we’ll make specific announcements in the coming days."

Chicago reissued its indoor mask mandate on Friday. Cook County followed suit on Monday. 

This comes also after Cook County Board President Toni Preckwinkle issued an executive order Friday requiring all county employees be vaccinated by Oct. 15. Chicago Public School employees also have until Oct. 15 to be vaccinated unless they qualify for a religious or medical exemption. 

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In New York City, all city employees will be required to show proof of vaccination or be subjected to weekly COVID testing come mid-September. Mayor Bill de Blasio made those announcements in July.