Does flu shot really prevent deaths?

Studies say the vaccines make a difference, but no one knows for sure even how many people die from the flu each year.

Health officials appealed for calm when some 50-million doses of flu vaccine vanished overnight. They tried to explain how it happened, who could get shots, how to keep the flu at bay.

But they can't answer one question.

Will more people die?

One reason nobody knows is the nature of the disease itself. Flu is complex and unpredictable.

"I'm wringing my hands over that hourly," said Dr. Greg Poland, director of the Mayo Clinic Vaccine Research Group, a member of the CDC's advisory committee on vaccines. "It depends on things we can't directly observe."

Another reason: No one knows how many people die from the flu in any year.

Federal officials and the media routinely use the same figure: 36,000 deaths a year.

But that number really is an average of the estimated number of flu deaths from 1976 to 1999. There were wide swings in those numbers each year - from 7,608 in 1978-79 to 72,399 in 1997-98.

And the numbers have steadily increased. During the past 10 years of the study, an average of almost 49,000 people died each year.

Are the number of deaths still going up? It's hard to know.

Tommy Thompson, secretary of the Department of Health and Human Services, has tried to reassure people about this year's shortage by saying it's not a crisis. Five years ago, he says, only 35- to 40-million Americans got shots. So going from 100-million to about 60-million shouldn't be that big a deal.

Actually, federal numbers show that more than 76-million shots were distributed five years ago. Still, the shots have steadily increased, to 83-million last year and an expected 100-million this year.

Which begs a question: Do Thompson's remarks mean those millions of shots added over the past five years haven't made a difference? Do the shots help prevent deaths?

Studies say they do. Bill Thompson is the epidemiologist with the federal Centers for Disease Control and Prevention who has led the flu death tally. He pointed to studies of smaller groups, showing people who got shots had half as much risk of dying as people who didn't.

"We assume there's a positive effect of the flu vaccine, based on the positive effect of the studies," he said.

But Thompson acknowledged those studies aren't definitive. Nobody has published an actual count of how many people have died since 1999. And different factors could affect how many lives are lost.

"There are a couple of things going on," Thompson said. "The vaccine (rate) is increasing, but the population is getting older and older, so we're more vulnerable."

Some flu experts think the CDC figures undercount the damage flu inflicts.

"An 85-year-old gets influenza today," Poland said. "A week from now, he gets pneumonia. He's put in the hospital and has a heart attack."

The death gets recorded as a heart attack, not a result of the flu.

Knowing the death toll isn't just an academic question for scientists, said Dr. William Schaffner, chairman of the preventive medicine department at the Vanderbilt University School of Medicine and a board member of the National Foundation for Infectious Diseases.

"Isn't that a great frustration?" Schaffner asked. "It's become apparent that we need to do a better job of tracking influenza hospitalizations and influenza deaths. It turns out it's a lot of work."

In normal years, doctors such as Schaffner beg patients and harangue the public to get flu shots - with limited success. Less than half the people in high-risk groups typically get the shot.

To convince people the shots really help takes real numbers, Schaffner said.

"If we have any intention to expand the current vaccination program, we're going to have to justify it with good, solid data," he said.

The CDC figures are the most recent published estimates for flu deaths. Because flu deaths don't have to be reported directly to health departments, the CDC analyzes data from national health statistics. That's the reason for the time lag.

The CDC already has made some changes. Prompted by the deaths of several Colorado children last year, the agency has stepped up surveillance of flu deaths among children.

For now, flu experts must wait to see what the disease will do. The news has been good so far. The CDC reported last week that the season has started slowly. And the strains that are circulating appear to be a good match for this year's vaccine, meaning it should provide more effective protection against the disease.

Different factors can combine to magnify the flu season's effects, said Dr. John Sinnott, director of the Florida Infectious Disease Institute at the University of South Florida. Cold weather makes the flu season worse by driving people inside, where closer contact and dry heat both make infection more likely.

"The perfect storm would be that No. 1, (a severe strain of) flu starts infecting people, No. 2, it's a cold winter, and No. 3, there's no vaccine," he said. "So far we only have one of the three."

Still, scientists are uneasy. Many are looking to Asia, where bird flu has killed more than two dozen people this year. The victims appear to have contracted the disease by handling chickens.

But scientists fear the bird flu could mutate and begin spreading from person to person. That would set the stage for a global pandemic, similar to the 1918 epidemic that killed 20-million to 50-million people around the world.

If that were to happen, current vaccines would provide little protection. Health officials have started work on a vaccine to protect against bird flu.

A less remote threat for this winter could come from the south. Another strain of flu is circulating in the Southern Hemisphere. If it moves north, this year's vaccine will be less effective.

"Take a scenario where (the new strain) roars out of nowhere, and we could have a bad year," Poland said.

One thing reassures Poland. Even if this year's flu season is bad, people are now far more likely to get antiviral treatments, such as Tamiflu, than they were just a few years ago.

"Five years ago, that didn't exist," Poland said. "Physicians themselves would get influenza and not know to take" such medication.

But even a mild season could have its downside. If this year's season passes uneventfully, Sinnott will be among the flu experts who breathe a sigh of relief. But he thinks federal officials have tried too hard to calm people's fears about the shortage by minimizing the benefits of the flu shots.

"There is a middle ground between (telling people), "There's a crisis,' and "Things are fine,"' he said. "If it's a mild year, people get the message that we really don't need to be vaccinated."

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