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Mortality Benefit of Repeat Flu Vaccination in Elders

... and a timely validation of this year's flu vaccination policy

The benefits of flu vaccination are well known, but the additive benefits of yearly vaccination have been surprisingly difficult to quantitate. Researchers in the Netherlands analyzed mortality rates for 26,071 outpatients (age, 65 or older) according to how many yearly flu vaccinations they had from 1996 to 2002.

Although a first vaccination reduced the mortality rate by a nonsignificant 10% compared with no vaccination, any revaccination reduced the mortality rate by a significant 24%. This effect was strongest during the flu season, and became insignificant during the summer. A nonsignificant trend suggested that mortality rates would decline further with each successive vaccination. Reduction in mortality rate with repeat vaccination was not significant among people who were 65 to 69, but became so among those who were 70 or older.

Although the mortality benefit was most pronounced among people without chronic illnesses, missing an annual vaccination was associated with a surge in mortality rate only among those with chronic illnesses. When yearly vaccination was resumed, the mortality rate in this group again declined.

Comment: The additive protection of yearly flu vaccination has been difficult to prove; this observational study cannot establish causality but does associate a cumulative survival advantage among healthy elders with yearly vaccinations. The findings also provide a timely validation of this year's flu vaccination policy: Patients with comorbidities who generally get flu vaccines should have priority in not missing a year's dose, whereas healthy people are unlikely to suffer serious consequences from going without vaccination for a year.

— Abigail Zuger, MD

Published in Journal Watch General Medicine November 26, 2004

Citation(s):

Voordouw ACG et al. Annual revaccination against influenza and mortality risk in community-dwelling elderly persons. JAMA 2004 Nov 3; 292:2089-95.

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