The risk-benefit analysis should be carefully considered by the person contemplating accepting the vaccine.

I thought the hospital management, employee health department, or infection control practitioner – whoever was making the pitch – should say the reason for being vaccinated was to protect our patients, to avoid acting as vectors of transmission of influenza from sick patients to those who were not sick with the flu but were susceptible.

As it turns out, the effectiveness of vaccinating health care workers as a way of protecting their patients is a matter of some controversy. It is intuitively appealing. It makes sense. From what we know about contagion and public health and health care associated infections, it just has to be true. But it’s not so easy to study, and the available evidence is not compelling.

And that brings us to the subject of this essay: mandatory vaccination.

The Centers for Disease Control and Prevention (CDC-P, or just CDC for short) currently recommends that everyone (past the age of 6 months) get the flu vaccine. I have to assume the rationale is that it will reduce the total societal burden of influenza illness during flu season.

But people don’t find that persuasive. They want to hear that it will keep them from getting sick. So that is the message. If the messengers are being responsible, they will include the caveat that the vaccine isn’t 100%, and it’s still important to pay attention to hygienic measures that reduce contagion.

But they aren’t as reserved in their recommendation as the facts suggest they should be. There are important limitations with this vaccine. The influenza virus is constantly changing. For those who have not studied virology, don’t worry, I’m not going to torture you with the details. But the proteins that make up the viruses mutate and rearrange, producing minor and major shifts, and occasionally new (“novel”) strains cross from other animal species to humans. The vaccine produced each year covers just a few strains, chosen based on a best guess of what strains will be in circulation. Those guesses aren’t always right.

With any vaccine, some people will be non-responders: the immune system just doesn’t make antibodies in response to the vaccine, at least not enough to be protective against illness.

And unfortunately the elderly, who are at greater risk of becoming seriously ill with the flu, are also at greater risk of being non-responders.