Sanford Health says it will require influenza vaccination for all employees.
Voluntary flu vaccination hasn't worked, said Director of Infection Control and Prevention Dr. Paul Carson. Only about 70 percent of employees were vaccinated under a voluntary program, he said.
Carson said more than 90 percent of employees should be vaccinated to protect patients from influenza.
"The patients that we come in contact with through our hospital and our clinics are really the most vulnerable people to influenza and it's more potentially severe effects," Carson said. "We want to maximize the potential to prevent them acquiring or coming in contact with influenza in our health care setting."
Employees can opt out for medical or religious reasons. They will be required to wear a mask during flu season. Employees who refuse the vaccine for other reasons will be furloughed.
Sanford has 26,000 employees and operates hospitals and clinics across the Dakotas and Minnesota.
Carson said the Centers for Disease Control and the American College of Physicians are among the organizations advocating mandatory vaccination of health care workers.