No Reduction in Deaths After Flu Vaccine in Elderly
No reduction outside flu season once other factors are considered
WEDNESDAY, Sept. 10 (HealthDay News) -- Influenza vaccination in the elderly does not reduce the likelihood of death outside flu season once other factors are taken into account, researchers report in the Sept. 1 issue of the American Journal of Respiratory and Critical Care Medicine.
Dean T. Eurich, Ph.D., and colleagues from the University of Alberta in Edmonton, Canada, examined the effect of flu vaccination on mortality outside flu season in 704 older patients hospitalized for community-acquired pneumonia, of whom half had been vaccinated and half had not been vaccinated. Twelve percent of patients died.
The researchers found that after adjusting for age, sex and comorbidities, vaccination significantly reduced the likelihood of death outside flu season (8 versus 15 percent, adjusted odds ratio 0.45). However, further adjusting for confounding (functional and socioeconomic status) erased much of this benefit and the reduction was no longer statistically significant (adjusted odds ratio 0.81).
"The 51 percent reduction in mortality with vaccination initially observed in patients with pneumonia who did not have influenza was most likely a result of confounding," Eurich and colleagues conclude. "Previous observational studies may have overestimated mortality benefits of influenza vaccination."
The study received support from Abbott Canada, Pfizer Canada, and Jannsen-Ortho Canada.