The 10-year study of seniors included those from the Portland area. It found that vaccination against influenza was associated with a 27 percent decrease in the risk of hospitalization for influenza or pneumonia - a common complication of the flu. The risk of death fell 48 percent.

The report was in Thursday's New England Journal of Medicine.

Roughly 60 percent of adults older than 65 are vaccinated against influenza each year, according to the federal Centers for Disease Control and Prevention, well below the national goal of 90 percent.

Manufacturers have shipped more than 400,000 doses of influenza vaccine to Oregon, and health officials want high-risk groups to protect themselves against the virus.

The elderly are more at risk of serious complications from the flu because they are more likely to suffer from chronic lung or heart problems, said Gary Oxman, health officer for Multnomah, Washington and Clackamas counties.

"For people with existing lung or heart disease," Oxman said, "the flu can produce enough of a compromise in the ability to get oxygen that it can lead to heart problems or respiratory failure."