Finally, a substantial proportion of illness with flu-type symptoms – collectively called “influenza-like illness” –is caused by viruses other than the influenza virus. The vaccine affords no protection whatsoever against those. At the peak of flu season, about half of all influenza-like illness is caused by those other viruses.

So it’s easy to see why it’s not a certainty that vaccinating health care workers protects their patients and why it might be challenging to study it and try to prove it one way or the other.

At my hospital, employees are encouraged to get the vaccine. If they decline, they are asked why. If their reason doesn’t square with what is known about the vaccine – for example, some people are convinced you can get the flu from the vaccine, which simply isn’t true for the injectable version, because the virus has been inactivated – they are given information and asked to reconsider. But vaccination isn’t compulsory.

Recently ABC News reported on the firing of a nurse in Indiana who refused influenza vaccination. She thought she had a legitimate reason for refusing: She said her belief that she had a right to protect her body from this foreign substance could be likened to a religious belief, and religious exceptions were permitted. Some infection control specialists don’t believe in religious exceptions. They think people whose religious beliefs preclude vaccination shouldn’t be taking care of patients in a hospital.

Frankly, I don’t have an opinion on religious beliefs about vaccination. I don’t know enough about them to have an informed opinion, and I don’t think I should have uninformed opinions.

But this much I do know: the principle that vaccinating health care workers against influenza protects their patients is based on a consensus of expert opinion, not compelling scientific evidence. A consensus of expert opinion may be a sufficient basis for recommendations. It is not a sufficient basis for compulsory vaccination.

It is time to start being honest about the difference between what we think is a good idea and what is supported by a solid foundation of medical science. And it is time to start making policy decisions that may violate individual autonomy as though we understand that difference.

Dr. Solomon teaches emergency medicine to residents at Allegheny General Hospital in Pittsburgh and is Medical Editor in Chief of ACEP News. He is a social critic, political pundit, and blogs at www.bobsolomon.blogspot.com.