Flu-shot benefit overstated?

The benefits of flu shots for elderly people have been greatly exaggerated, according to researchers at Seattle's Group Health Center for Health Studies and George Washington University in Washington, D.C.

Even so, the elderly should continue to get vaccinated against influenza because "even a partly effective vaccine would be better than no vaccine at all," researchers wrote in the report, published Monday in The Lancet Infectious Diseases.

Many countries, including the U.S., urge those 65 and over — who account for about 90 percent of flu-related deaths — to get flu shots to ward off flu complications.

That public policy has been based on flimsy — even nonexistent — evidence, these researchers conclude.

"The message is: We should not be basing our vaccine policy on data that is faulty," said Dr. Lisa Jackson, a study author and investigator with the Group Health center.

Many studies undergirding health policy report that flu shots reduced total wintertime risk of death by 50 percent.

That can't be correct, Jackson said. "Influenza doesn't cause half of all deaths, so vaccine couldn't have created that big an effect," she said.

"We find it peculiar that the claims that influenza vaccination can prevent half — or more — of all winter deaths in elderly people have not been more vigorously debated," wrote Jackson and Dr. Lone Simonsen of George Washington University, the lead author of their report, "Mortality benefits of influenza vaccination of elderly people: an ongoing controversy."

In studies at Group Health, Jackson found that unvaccinated seniors died at a higher rate for reasons unrelated to flu.

The authors also note that increasing vaccination rates since 1980 have not lowered death rates among the elderly.

These researchers ask: How could previous studies have been so wrong?

In part, they conclude, because the studies simply compared people who got a flu shot with people who didn't, after the fact. And it may be that sicker, frail elderly people were more likely to skip flu shots.

In addition, the studies looked only at the flu-season period, using a long-standing but indirect method of assessing flu-related deaths.

When Group Health researchers studied their own patients last year, they found the risk of death among vaccinated elderly during the winter flu season was half that of those who weren't vaccinated — just like the previous studies showed.

But looking at the rest of the year, they found unvaccinated elderly still died at much higher rates than those who had flu shots — for reasons unrelated to flu, Jackson said.

Dr. Jeff Duchin, director of communicable-disease control for Public Health — Seattle & King County, said at least one study cited by the researchers showed some reduction in death rates for people age 70 and older.

"The bottom line is: The virus kills hundreds of thousands of people every year, and the vaccine works," Duchin said. "The researchers are debating about how best to measure that. But people need to understand they get protection from the vaccine."

On average, antibody response to the vaccine, necessary to confer protection against the flu, declines as people age, Jackson noted. But researchers don't know how much response is necessary to prevent flu.

And seniors are a diverse group, she added. "In their 70s, some are climbing Mount Rainier, and others are bedridden."

For now, the researchers say, elderly people should continue to get flu shots, because there is little risk. "We're not saying we should reverse our policy," Jackson said. "We know the vaccine prevents the flu in some people, and that likely includes some seniors."

But a more realistic assessment of the vaccine's benefits, she said, may push researchers to begin studying other strategies to help the elderly avoid flu and its complications.

Carol M. Ostrom: 206-464-2249 or costrom@seattletimes.com