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Influenza Vaccination Can Prevent Cardiac and Cerebrovascular Events

In this large cohort study, vaccination protected elders against hospitalization and death.

Influenza vaccination reduces rates of respiratory illness and death in elderly people. Because influenza epidemics are associated with increases in hospitalizations for cardiac and cerebrovascular events, researchers pooled data from 3 managed care organizations to determine whether influenza vaccination prevents these outcomes.

In 1998-1999 and 1999-2000, nearly 60% of about 140,000 elders (age, 65 or older) received influenza vaccinations during each of the 2 influenza seasons. In analyses that were adjusted for baseline clinical differences between vaccinated and unvaccinated cohorts, vaccination was associated with approximately 20% fewer hospitalizations for cardiac and cerebrovascular events during the 2 influenza seasons. The vaccinated cohorts also were 30% less likely to be hospitalized for pneumonia or influenza and were 50% less likely to die. During control periods, when influenza was absent (June through September), vaccinated subjects did not experience lower hospitalization rates than did unvaccinated subjects.

Comment: Because there were numerous differences in baseline characteristics between vaccinated and unvaccinated subjects, these results might reflect residual confounding despite statistical adjustments. However, vaccinated subjects generally had more baseline comorbid conditions than did unvaccinated subjects, which would tend to minimize the benefits associated with vaccination. Thus, the study's positive results are probably legitimate and should serve as further impetus to recommend vaccination to elders.

— Allan S. Brett, MD

Published in Journal Watch General Medicine April 18, 2003

Citation(s):

Nichol KL et al. Influenza vaccination and reduction in hospitalizations for cardiac disease and stroke among the elderly. N Engl J Med 2003 Apr 3; 348:1322-32.

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