OTTAWA -- Ottawa's largest transit union warns 400 to 500 OC Transpo workers could face suspension next month for failing to get the COVID-19 vaccine.

The city of Ottawa's vaccination policy requires all employees, contractors, students and volunteers at the city to be fully vaccinated by Nov. 1.

The Amalgamated Transit Union, which represents OC Transpo drivers, dispatchers and mechanics, says many of its members may not be vaccinated by the deadline.

"It's not only the operators, it is maintenance so that is going to have an impact on service as well as bus operators and Para Transpo operators as well," said Clint Crabtree, president of ATU Local 279.

The ATU filed a grievance with the city of Ottawa over the mandatory vaccination policy.

"As a union, we're protecting the rights of our members and our concern is that it's being forced on our members that don't want to receive it for various reasons," said Crabtree.

During Wednesday's council meeting, Coun. Carol Anne Meehan said she heard that 20 per cent of drivers would be unable to work due to their vaccination status, which could cause disruptions with the transit service.

Meehan asked staff if there was a plan in place to ensure there will be no disruptions in transit service.

"We are working closely with Ottawa Public Health," said Acting OC Transpo General Manager Michael Morgan, noting employees now can upload their vaccination status.

"We are planning on using that to essentially inform and understand what the impacts are going to be after Nov. 1, if any. At this point, early indication is we don't believe there's going to be."

Morgan says it will have a better understanding on a possible impact to service on Nov. 1.