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For decades, public health officials have touted the benefits of vaccinating people older than 65 against influenza. But new research has cast doubt on the wisdom of these policies.

While influenza may seem relatively benign, it is nevertheless a big killer. About 4,000 to 8,000 Canadians die each year of the flu, according to the Public Health Agency of Canada. (Technically, they die of complications such as pneumonia, but influenza is the trigger.) The majority of these fatalities occur among seniors.

In many jurisdictions there are aggressive immunization programs that ensure the vast majority of seniors get an annual flu shot.

Policy makers have been guided by research that suggested vaccination of people older than 65 had tremendous benefits. Studies consistently showed that those who were vaccinated were half as likely to die of the flu as those who were not.

How could we deny those benefits to Granny and Gramps? So jab them we did.

Alas, it seems the eye-popping benefits of flu shots were a little too good to be true. While influenza vaccination rates have climbed steadily, there has been no appreciable reduction in deaths.

New research helps explain why.

The main culprit seems to be the healthy user effect, and the way researchers initially tried to compensate for it. Simply put, people who are in good health are most likely to get their annual flu shot. Those who are frail, have mobility problems and other health issues are less likely to get vaccinated. Not surprisingly, the healthy people are less likely to die. But this probably has little to do with their flu shot.

The initial studies that found huge reductions in mortality tried to adjust for the healthy user effect by looking for chronic illnesses such as cancer and heart disease. But a new paper by a team of researchers at the University of Alberta led by Sumit Majumdar shows, essentially, that these were the wrong measures. Rather, the best predictors of who would die from influenza/pneumonia were little things such as whether a patient needed help bathing and dressing, the kinds of medication they were taking and their lung function.

When the research team adjusted for these factors, they found little difference in the death rate among the vaccinated and unvaccinated.

There is also a growing body of evidence that the vaccine does not work as well in older people as in younger adults and children. Vaccines work by priming the immune system to recognize viruses and mount a response to the threat, but the immune system slows with age. One study showed that, as a result, people older than 70 may need four times the influenza antigen to get the same protection as younger people.

So what does all this mean?

For public health officials, this new evidence points to a need for a far more sophisticated influenza immunization strategy. Much more effort must be made to vaccinate the frail elderly and those with lung conditions such as chronic obstructive pulmonary disease and asthma, instead of aiming to immunize ever-larger numbers of relatively healthy people.

Manufacturers, for their part, need to improve their product. The flu vaccine does not cut the death rate by 50 per cent; rather, the real figure seems to be 20 per cent or less. That's not good enough.

The most important message that needs to be retained from these new findings, however, is that we need to do a much better job of ensuring the frail elderly do not get infected in the first place.

Practically, that means paying more attention to simple precautions. It seems trite to say it, but handwashing matters. It can be a matter of life or death.

We must be careful not to take from this research the idea that vaccinating the healthy is pointless. On the contrary, vaccinating people who are in regular contact with seniors is primordial, as it is one of the best ways to prevent exposure and transmission of the flu virus.

At the top of that list are health professionals. Physicians, nurses and support staff in hospitals, long-term care facilities and nursing homes must be vaccinated. Yet, rates of influenza vaccination in these settings are abysmally low.

Family members who visit their loved ones, particularly those who are not in the best of health - whether they are in hospitals, nursing homes, communal living facilities or living independently - should also get flu shots. This is particularly true of children, who, because of their interactions in school, are little flu-spreading machines.

So, should Granny still get her flu shot?

The short answer is: Probably. A little protection against influenza is better than none at all.

But more important is that Granny's caregivers and those who care deeply for her get a flu shot.