Research by Dr Lisa Jackson and colleagues at Group Health Co-operative, Seattle, found evidence of serious bias in estimates of influenza vaccine effectiveness in seniors. Their study suggests that the association between vaccination and risk of death is influenced by the fact that relatively healthy seniors (that is, those already less at risk from dying) are more likely to get vaccinated.

However, the research does not indicate that there is NO benefit in vaccinating the elderly, just that the differences in health between seniors who receive vaccine and those who do not make it difficult or impossible to tell what benefit is being derived from the vaccine.

A commentary on the papers also published today in the IJE argues that there are reasons to seek ways to augment current vaccination strategy, for example, vaccinating health care workers, nursing home personnel and school children, who are the major spreaders of flu within the community. This would further decrease flu deaths in the elderly by reducing transmission of the virus. It could be done while better vaccines for the elderly are developed along with the use of new technologies to better evaluate effectiveness.

Dr Jackson and colleagues studied 73,527 people aged 65 and over during an eight year period. They 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.

Since a protective effect of vaccination should be specific to flu season, they would expect to find reductions in risk of death or hospitalisation during the season. However, they found the greatest reductions in the period b
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Contact: Hannah Johnson
hannah.johnson@bristol.ac.uk
44-117-928-8896
University of Bristol
21-Dec-2005