Around 50 workers at a US health company have been fired after they refused to get the influenza vaccine ahead of the winter flu season.

Employees, students, volunteers and vendors at Essentia Health in Minnesota were told earlier in the autumn that they could either get the flu shot, provide a valid religious or medical reason for exemption with sign-off from a clergy member or doctor, or leave the company, which also has facilities in three other states.

Explaining why Essentia took a mandatory approach to the vaccines, Rajesh M. Prabu, chief of patient quality and safety, told WCVB: "Purely voluntary, or more education, doesn't get you those high levels of immunisation compliance."

According to Prabu, 99.5% of employees chose one of the first two options but approximately 50 people have now been terminated, with others still waiting to hear if their exemption will be approved. It is expected that more people will be fired.

The rule was designed to improve patient safety, Prabu added. "People may debate how effective that is. Based on what the level of evidence is and what our peers are doing, we thought this was the best way to protect our patients."

Minnesota Nurses Association is considering taking action against Essentia Health, for what they described as "unnecessarily intrusive" and possibly not even fully effective. "Minnesota Nurses Association is not against getting the flu shot. What we are against is making it mandatory," president Mary Turner told KVRR.

Turner said the spread of flu should be contained by ensuring health workers have adequate time off when they are sick, sufficient protective equipment in hospitals, and mandating constant hand washing. "See, it's a multi-facet thing. To just automatically say that 'Ooh, the flu shot is going to do it, that's inaccurate. We don't agree with that."

There is no state law in Minnesota requiring health care employees to get flu vaccines although it is strongly recommended.

The Center for Disease Control and Prevention in the US says the seasonal flu vaccination reduces the risk of influenza by between 40% and 60%. However, this effectiveness can vary depending on the subject's age and health, and how closely the flu virus circulating in the community matches the viruses the vaccine is designed to protect against.