Home » News » 12/05 » Benefits of flu vaccine 'substantially overestimated'

Benefits of flu vaccine 'substantially overestimated'

Date published: 21/12/2005

Studies of influenza vaccine effectiveness in elderly people substantially overestimate vaccine benefits, according to new research. According to Dr Lisa Jackson and her colleagues at Group Health Co-operative, Seattle, there is evidence of serious bias in estimates of influenza vaccine effectiveness in seniors.

Their study suggested that the association between vaccination and risk of death is influenced by the fact that relatively healthy older people (that is, those already less at risk from dying) are more likely to get vaccinated.

However, they did not say that there was no benefit to the vaccine regime, but that due to the differences in health between those who receive vaccine and those who do not, it is difficult or impossible to tell what benefit is being derived from the vaccine.

In a commentary on the studies, Professor Paul Glezen of Baylor College of Medicine, Houston, said: "During the period from 1989 to 1997 the vaccination rate for people aged over 65 in the US increased from 30 to 67 per cent. Despite this increase, mortality and hospitalisation rates continued to increase rather than decline as would be expected if the vaccine was optimally effective.

"The study by Dr Jackson and her colleagues concludes that elderly people who choose to take the vaccine are, contrary to the findings of earlier cohort studies, in better health than those who fail to get the vaccine. This suggests that better studies of the benefits of flu vaccine in elderly and other high-risk groups are necessary to guide strategies for flu control."

The study involved 73,527 people aged 65 and over during an eight year period. The researchers evaluated the association of flu vaccination and risk of death, and the association of flu vaccination and risk of hospitalisation for pneumonia, in periods before, during and after flu season.

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