Flu vaccine 'less effective than thought'

September 25, 2007

Giving elderly people a vaccine to prevent flu-related death is not as

effective as reports have suggested, according to a study published today.

Researchers state in the Lancet journal that the mortality benefits of

vaccination have been 'greatly exaggerated'.

In the UK, as in most high income countries, people aged over 65 are

recommended to be immunised against flu as they are more likely to have a

severe or complicated illness as a result of flu.

Dr Lone Simonsen of Washington University and colleagues argue that

the expressed benefits of such a system on mortality are greater than in

reality for two reasons.

They claim that the results are skewed as there is a 'frailty selection

bias' – where not-so-frail older people are vaccinated more often than their

infirm peers – and non-specific trial endpoints such as all-cause mortality

are used.

'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.

The researchers draw attention to studies which have shown that the clinical

benefits and antibody responses in older people decline after the age of 70.

But they warn that older people should not stop themselves from being

immunised.

'While awaiting an improved evidence base for influenza vaccine mortality

benefits in elderly people, we suggest that this group should continue to be

vaccinated against influenza,' the researchers conclude.

'Influenza causes many deaths every year, and even a partly effective

vaccine would be better than no vaccine at all.'

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