The benefits of vaccinating the elderly against influenza have been greatly exaggerated, according to a major review of the literature published in the latest issue of The Lancet Infectious Diseases.

Health policy in most Western countries aims to cuts flu deaths by targeting people aged at least 65 years for vaccination.

However, the authors from George Washington University, Washington DC, point out that although placebo-controlled randomised trials show the influenza vaccine is effective in younger adults, few trials have included elderly people, and especially those aged at least 70 years. This age group is supposed to account for three-quarters of all influenza-related deaths.

They add that recent excess mortality studies have been unable to confirm a decline in influenza-related mortality since 1980, even though vaccination coverage increased from 15% to 65% during this period.

Lead author, Dr Lone Simonsen, said: "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."

The authors suggest that deaths among older people that are assumed to be due to influenza might instead be due to accidents or other causes. They say further research should be done to see whether or not this is the case.

But caution advised in changing policy

Dr Simonsen said, however, it would not be wise to alter vaccination policy yet. "While awaiting an improved evidence base for benefits in elderly people, we suggest that this group should continue to be vaccinated against influenza. Influenza causes many deaths each year, and even a partly effective vaccine would be better than no vaccine at all.

"But the evidence base concerning influenza vaccine benefits in elderly people does need to be strengthened," he added.

Clinical trial experts Dr Tom Jefferson and Dr Carlo Di Pietrantonj, of Cochrane Vaccines Field in Alessandria, Italy backed the controversial use of randomised trials in elderly people to clarify the benefits of flu vaccination. "This is in our opinion the only ethical and scientific way to have definitive answer to the question of whether or not current influenza vaccines protect elderly people", they said.

In an accompanying editorial, The Lancet Infectious Diseases says: "We must never again allow layers of poor research to mask substantial uncertainty about the effects of a public-health intervention and present a falsely optimistic view of policy." Michael Day