The widely-held perception that the influenza vaccination reduces overall mortality risk in the elderly does not withstand careful scrutiny, according to a new report. 

The vaccine does confer protection against specific strains of influenza, but its overall benefit appears to have been exaggerated by a number of observational studies.

The new study included more than 700 matched elderly subjects, half of whom had taken the vaccine and half of whom had not. After controlling for a wealth of variables that were largely not considered or simply not available in previous studies, scientists found that any such benefit “if present at all, was very small and statistically non-significant and may simply be a healthy-user artifact that they were unable to identify.”

“While such a reduction in all-cause mortality would have been impressive, these mortality benefits are likely implausible. Previous studies were likely measuring a benefit not directly attributable to the vaccine itself, but something specific to the individuals who were vaccinated — a healthy-user benefit or frailty bias,” explains study coauthor Dean T. Eurich, PhD.

“Over the last two decades in the United Sates, even while vaccination rates among the elderly have increased from 15% to 65%, there has been no commensurate decrease in hospital admissions or all-cause mortality. Further, only about 10% of winter-time deaths in the United States are attributable to influenza, thus to suggest that the vaccine can reduce 50 percent of deaths from all causes is implausible in our opinion.”

American Journal of Respiratory and Critical Care Medicine – September 2008;178:527-33.

http://ajrccm.atsjournals.org/