MINNEAPOLIS (MCT) — Flu shots for the elderly has been a health-care mantra for years. Doctors insist on them. The federal government pays for them.

But behind that apparently united health front has been a growing debate about whether the benefits of flu shots for the aged have been greatly exaggerated. After all, although vaccination rates among the elderly have skyrocketed in the past two decades, deaths and hospitalizations of older people from flu haven't budged.

Now, a study led by Dr. Kristin Nichol at the Minneapolis Veterans Medical Center has provided the latest word on the subject.

The vaccine not only works, she found. It works really well.

The massive study published online Thursday in the New England Journal of Medicine shows that over 10 flu seasons the vaccine reduced the risk of hospitalization for older people by 27 percent, the risk of death by 48 percent.

That doesn't mean that 48 percent of those who get the shot are avoiding death. The rate of hospitalization and death from flu is extremely small. But among that very small group, flu shots appear to better protect older people from flu-induced hospitalization and death.

"This study trumps them all," said Dr. Greg Poland, an infectious disease specialist at the Mayo Clinic, who was not involved the research.

The results are not likely to end the discussion, however. Other flu experts say that tracking real people who don't get the vaccine is an inherently flawed way to measure how well it works.

"Healthier people are likely to seek out the vaccine," said Dr. Lisa Jackson, an infectious disease researcher at the Group Health Center for Health Studies in Seattle. "If so, the vaccine group has a lower risk ... purely because they started out healthier."

No one is suggesting that elderly people should stop getting flu shots. It's still the only thing that's been proven to help prevent the flu.

"There are always naysayers." said Pat Mayfield, 78, who's gets a flu shot every year. "My attitude is, whether it works or not, it's just in case."

But Jackson and others say that almost nothing is known about the real benefits for people aged 70 and older.

Elderly people are targeted for vaccines because they account for three-fourths of all flu-related deaths. But they also are the least likely to be protected by the vaccine because the body's immune system weakens with age.

"The absolute benefit is unknown," Nichol said. Still, she and her fellow researchers did everything they could to eliminate those problems that would lead to misleading conclusions.

The study tracked about 500,000 people aged 65 and older living at home in four parts of the country, including HealthPartners members in Minnesota and western Wisconsin. Some in the study were followed for only one year, and others were followed for longer.

Over 10 years they tracked a total of 713,000 outcomes. And using computer analysis, they adjusted the vaccinated and unvaccinated people for health conditions so the groups were, medically speaking, balanced.

In the unvaccinated group, seven-tenths of 1 percent were hospitalized, compared to six-tenths of 1 percent in the vaccinated group. And 1.6 percent of the unvaccinated group died, compared to 1 percent in the vaccinated group.