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CHICAGO — Some big-city mayors and large companies are issuing tougher restrictions on COVID-19 vaccinations.

New York City became the first major American city Tuesday to require proof of vaccination for indoor dining and gyms.

In Denver, Mayor Michael Hancock announcing vaccination requirements affecting tens of thousands of workers — and they’re not alone.

“I am approving a far-reaching health order mandating that all city employees, as well as private-sector workers in high-risk settings, be required to be fully vaccinated against COVID-19 by September 30,” Hancock said.

More than a dozen big companies are requiring their employees, at least those working in the office, to provide proof of vaccination — Microsoft and Tyson Foods being the latest.

In Chicago, real estate developer Related Midwest is requiring all workers to receive at least their first dose of the vaccine by August 31, or look for another job.

A company spokesperson told WGN in a statement, “the goal is to keep employees and their families safe as they are back in the office.”

Read more: Latest Chicago news headlines

Employment attorney Robert Duston says while employers cannot ask for personal medical information, they can require proof of vaccination for continued employment.