Fueling a flu debate: do vaccinations save lives among the elderly?

It would seem to be a no-brainer: Vaccinating elderly people against influenza each fall should lead to fewer hospital stays and higher survival rates. But past studies haven't established such trends.

Researchers now report that elderly people who get flu shots indeed appear less likely to die or to become hospitalized during the flu season than those who don't get immunized.

Flu shots limit illness in most age groups but have shown an inconsistent effect in the elderly. And even though flu vaccine coverage of elderly people in the United States grew from 15 percent in 1980 to 65 percent by the mid-1990s, no corresponding drop in the death rate was reported.

Nevertheless, public policy in most Western countries calls for vaccinating the elderly. Ironically, the assumed benefit prevents researchers from conducting a trial in which some older people get shots and others get placebo injections, because not giving flu shots to some study participants would violate ethical standards. This means that scientists can only analyze data drawn from the community, in which elderly people choose whether or not to get immunized.

In the new study, researchers used U.S. and Canadian medical records to review the rates of thousands of people age 65 or older during 10 consecutive winter flu seasons. Starting in 1990, the records identified who got flu shots, revealed each person's medical history, and showed who had died or been hospitalized, says Kristin L. Nichol, a physician and epidemiologist at the Veterans Affairs Medical Center in Minneapolis. She and her colleagues thus assessed more than 700,000 personal flu seasons.

People who got shots during a given flu season were one-fourth less likely to be hospitalized for the flu or pneumonia and half as likely to die of any cause during that season as were unvaccinated people, the team reports in the Oct. 4 New England Journal of Medicine.

To test whether elderly people who chose to be vaccinated might be healthier than those who didn't, the researchers checked hospitalization visits during the summer, when flu isn't a factor. They found no difference between the two groups.

"This is the most comprehensive study of this type I've ever seen," says John D. Treanor, an infectious disease physician at the University of Rochester (N.Y.) Medical Center. "The vaccine's got to be doing something," he says, "but I think there are some legitimate doubts about the magnitude of the shots' effects."

Epidemiologist Lone Simonsen of George Washington University in Washington, D.C., says that because the study tabulates deaths from all causes, it sheds little light on the effect of the vaccine. "You need to look at pneumonia-related deaths specifically," she says. Nichol says, however, that death certificates seldom mention influenza, so the disease leaves a poor paper trail.

Simonsen also notes that elderly people who are especially frail might be less likely to get out of their homes than their healthier peers are, and therefore less apt to receive vaccinations. But Nichol says that the vaccinated people in the study were more likely than the others to have diabetes or heart problems, yet showed better survival. The study's findings are "robust," she concludes.