Bias alone could account for benefit attributed to flu vaccine, study finds

BMJ 2008; 337 doi: (Published 03 September 2008) Cite this as: BMJ 2008;337:a1550
  1. Jeanne Lenzer
  1. 1New York

    The reduction in mortality seen among elderly people who have been given the flu vaccine could have more to do with a “healthy user” effect than any protective value of the vaccine itself, a study has found.

    The researchers, from the University of Alberta in Edmonton, Canada, prospectively obtained clinical, laboratory, and functional status data and identified 1813 adults with community acquired pneumonia who were admitted to six hospitals in Alberta (American Journal of Respiratory and Critical Care Medicine 2008;178:527-33, doi:10.1164/rccm.200802-282OC). Of these adults, 354 vaccine recipients met the inclusion criteria and were matched with 354 controls.

    The outcome of in-hospital mortality was examined during the months before and after the flu season, when no benefit of the flu jab would be expected.

    The researchers replicated a 51% mortality difference between the …

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