Protesters carrying signs and chanting "we will not comply" gathered on LaSalle Street as an ordinance was introduced to revoke the mandate.
Chicago police union president John Catanzara said Lightfoot has overstepped her boundaries, and that the fight is not about the actual vaccine.
"This has always been about union protections and the city’s obligation to come to the collective bargaining table and negotiate what policies are going to look like, especially when it affects peoples paychecks," Catanzara said.
The ordinance introduced Monday would reverse the mandate, pay officers now on "no-pay" status retroactively, and require any policy that puts city employees on "no-pay" status to be approved by the full council going forward.
A wife and mother of Chicago police officers who carried a poster with their pictures during the protest said her son turned in his badge rather than get the shot.
"It’s so unfair. My son did a wonderful job all these years and for them to do this to him, it’s uncalled for," said Donna Felmon.
Lightfoot has said she’ll do everything in her power to stop any vaccine repeal. Supporters of the vaccine have said it is unfair for unvaccinated coworkers to put them at risk.
But critics say if it’s about public safety, it's misguided.
"If firing police and firemen and healthcare professionals is about public health, then what does an assault on public health look like," said Sharon Sikora.
Lightfoot has called the effort "foolishness" and has said she will do everything in her power to block it.