A Minnesota-based health system has fired about 50 employees who refused to get a flu shot.

Essentia Health announced in October that employees would be required to get vaccinated for influenza unless they received a religious or medical exemption.

The company said it wanted to help keep patients from getting sick at its 15 hospitals and 75 clinics in Minnesota, Idaho, North Dakota and Wisconsin.

Essentia says 99-percent of the company's 13,900 eligible employees had gotten the shot, received an exemption or were getting an exemption by the November deadline.

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

More recently doctors in the Denver area reported an increase in the number of flu cases. Dr. Comilla Sasson tells 9NEWS that the majority of cases she's seen over the past couple weeks are influenza A. The trouble is that the vaccine, she says, is better at protecting people from influenza B.

We also talked with Dr. Lindsey Cassidy with Rose Family Medicine in Denver Monday. She says it's still really important for everyone over the age of 6-months to go ahead and get that flu shot, especially those considered high-risk.