ST. LOUIS (AP) — A St. Louis hospital says at least one employee has been fired for violating a policy requiring flu vaccination.

The St. Louis Post-Dispatch reports that the policy prompted a protest Tuesday outside Mercy South. Protest organizer Nelia Aubuchon says the fired employee is a nurse who had been granted a religious exemption from the annual flu shot while working for St. Anthony’s Medical Center before it was acquired by Mercy this year.

Mercy implemented its flu shot policy in 2016. The hospital said in a statement that most requests for medical or religious exemptions were granted. Employees whose exemptions were declined were notified this week. The statement says the policy “saves lives.”

More than two-thirds of hospitals in the U.S. require their employees to get flu shots.