The benefits of giving the flu vaccine to elderly people have been greatly overstated, conclude authors of a review in The Lancet Infectious Diseases.

The authors, led by Dr. Lone Simonsen of George Washington University in Washington, D.C., say most of the studies suggesting that the vaccine prevents deaths in the elderly are weak.

Most provinces in Canada, as well as many other countries, encourage all citizens over the age of six months to get the flu vaccine. Those over the age of 65 are considered to be at high risk for developing the flu and its related complications.

Many clinical studies have shown that the flu vaccine is effective in younger adults. But the authors point out few studies have included elderly people, and especially those aged at least 70 -- the age group that accounts for three-quarters of all influenza-related deaths.

"The remaining evidence base is currently insufficient to indicate the magnitude of the mortality benefit, if any, that elderly people derive from the vaccination programme," they write.

Although vaccination coverage increased from 15 per cent to 65 per cent since 1980, recent studies have been unable to confirm that has resulted in fewer influenza-related deaths among the elderly.

"That is a problem, because that is where most of the influenza death are," said Simonsen.

The problem with the studies that have been done is that they include deaths of all causes, but don't specifically look at deaths caused by influenza, the authors say.

"Paradoxically, whereas those studies attribute about five per cent of all winter deaths to influenza, many cohort studies report a 50 per cent reduction in the total risk of death in winter--a benefit ten times greater than the estimated influenza mortality burden."

As well, the authors note, there has been some evidence that the elderly suffer from "immune senescence" -- that is, their bodies no not mount an adequate immune response as they age, so the vaccines do not protect them against an attack by a flu virus.

Nevertheless, the authors say they believe the elderly should continue to get flu shots.

"Influenza causes many deaths each year, and even a partly effective vaccine would be better than no vaccine at all," they write.

Infectious disease expert Dr. Neil Rau notes that The Lancet review didn't look at how effective the vaccine has been at preventing illnesses and hospitalizations -- which are also important factors to consider when measuring the vaccine's worth.

But both Rau and the authors agreed that what is needed is more reliable research on the vaccine's effectiveness in seniors.

"Once something gets adopted by public health authorities worldwide, it's something that becomes un-discussable," Rau told CTV News. "And it's high time we had that discussion."

With a report by CTV's Jed Kahane