Flu Vaccine Does Protect Older People

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The new study began in 1990 and included data through the 1999-2000 flu season for people from 18 different groups of community-dwelling elderly members of one health maintenance organization. Additionally, information on members of two other HMOs was included from 1996 through 2000.

The study included almost 300,000 unvaccinated people and more than 415,000 vaccinated individuals. All were over 65 years old.

In the entire study group, there were 4,599 hospitalizations and almost 9,000 deaths from influenza during the 10-year study period. On average, hospitalization rates were 0.7 percent for unvaccinated people and 0.6 percent for those vaccinated. On average, death rates were 1.6 percent and 1.0 percent, respectively.

The researchers found that those rates varied from flu season to flu season, with more hospitalizations and deaths occurring in years when the flu vaccine wasn't a good match against the strains of circulating flu.

The researchers also looked to see if hospitalizations and death rates were lower in the summer, which would suggest that the effect wasn't from the vaccine. They didn't find such an association, suggesting that the reduction during influenza season was, in fact, due to the vaccine.

"This is the most definitive look linking outcomes to vaccination status," Treanor said.

Nichol said: "I think this study goes a long way to addressing concerns and shows what the influences of the influenza vaccine might be even after taking into account age, health conditions and previous hospitalizations."

She added that, in addition to preventing hospitalizations and deaths, the flu vaccine is "highly cost-effective and even cost-saving."

More information

To learn more about flu vaccine, visit the U.S. Centers for Disease Control and Prevention.