Annual flu shot cuts all-cause deaths in elderly

Compared with a first vaccination, yearly re-vaccination against influenza is associated with a reduction in the annual risk of dying from any cause among individuals 70 years of age or older, Dutch investigators report.

There have been no large studies that looked at the benefit of annual re-vaccinations, Dr. Bruno H. Ch. Stricker, from Erasmus University Medical Center in Rotterdam, and colleagues explain in this week's Journal of the American Medical Association.

They therefore conducted a population-based study using a computerized database that included 26,000 community-dwelling individuals age 65 or older, followed from 1996 to 2002.

During the study period, when flu seasons were mild to moderate, 3485 subjects died. Annual flu vaccination rates ranged between 64 percent and 74 percent.

The first vaccination was linked to a reduction in annual mortality risk of 10 percent, which was not significant from a statistical viewpoint. Any re-vaccination was associated with a 15 percent reduction, which was strongest during epidemic periods at 28 percent.

If people stopped getting an annual flu shot, their risk of dying increased significantly - by 25 percent the first year, up to 83 percent if continued. Once they started getting the vaccine again, however, the mortality risk fell back to a level similar to that seen following re-vaccination.

"In the total population 1 death was prevented for every 302 vaccinations, or 1 for every 195 revaccinations," Stricker's group writes.

"This study supports the recommendation for yearly influenza vaccination for elderly individuals," they conclude. This applies not only to people with underlying illness but also to healthy individuals, as well as people 80 years or older.

SOURCE: Journal of the American Medical Association, November 3, 2004.