DULUTH, Minn. (AP) — A Duluth-based health system has fired about 50 employees who refused to get a flu shot.

Essentia Health announced last month that employees would be required to get vaccinated for influenza to help keep patients from getting infected, or else receive a religious or medical exemption. The deadline was Monday.

Essentia says 99 percent of the company's 13,900 eligible employees have either gotten the shot, received an exemption or are getting an exemption.

The United Steelworkers filed an injunction to try to delay the policy from going into effect, but a federal judge denied that request. Minnesota Public Radio reports at least two other unions are filing grievances on behalf of workers who lost their jobs.

Essentia has 15 hospitals and 75 clinics in Minnesota, Idaho, North Dakota and Wisconsin.

"Patients and the community can be confident the expert care they receive at Essentia is taking place in a healing environment providing vital protection from influenza," said Dr. Rajesh Prabhu, Infectious Disease and Chief Patient Quality and Safety Officer at Essentia Health.

"The Minnesota Department of Health is on the record that there is no evidence to suggest that healthcare systems mandating flu shots see a significant reduction in influenza cases in their facilities.," a statement reads from the Minnesota Nurses Association.