New York City expanded its vaccine mandate to all employees Wednesday while Chicago began to place police officers who refused to disclose vaccine status on unpaid leave.

Cities that mandate Covid-19 vaccinations for municipal workers are beginning to crack down on employees who refuse inoculations, with some preparing to suspend or fire holdouts in the coming weeks.

Chicago pulled 21 officers off the street this week and suspended them without pay for failure to disclose their vaccination status, said Police Superintendent David Brown. The deadline for all city employees to enter their vaccination status into a city-run portal was Oct. 15. After that, unvaccinated employees were expected to undergo weekly coronavirus testing. But Chicago’s local Fraternal Order of Police encouraged officers not to disclose their vaccine status, arguing that the city should have been required to negotiate the requirements with the union.

The Chicago Police Department had the lowest response rate of any city agencies, followed by the fire department, according to data provided by the city. Approximately 67% of department employees had verified their vaccination status in the portal as of Tuesday, said Brown.