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FLU VACCINES AND THE HEALTHY USER EFFECT
Shannon Brownlee and Jeanne Lenzer, Atlantic - What if flu vaccines do not protect people from dying-particularly the elderly, who account for 90 percent of deaths from seasonal flu? And what if the expensive antiviral drugs that the government has stockpiled over the past few years also have little, if any, power to reduce the number of people who die or are hospitalized? The U.S. government-with the support of leaders in the public-health and medical communities-has put its faith in the power of vaccines and antiviral drugs to limit the spread and lethality of swine flu. Other plans to contain the pandemic seem anemic by comparison. Yet some top flu researchers are deeply skeptical of both flu vaccines and antivirals. Like the engineers who warned for years about the levees of New Orleans, these experts caution that our defenses may be flawed, and quite possibly useless against a truly lethal flu. And that unless we are willing to ask fundamental questions about the science behind flu vaccines and antiviral drugs, we could find ourselves, in a bad epidemic, as helpless as the citizens of New Orleans during Hurricane Katrina. . .
While vaccines for, say, whooping cough and polio clearly and dramatically reduced death rates from those diseases, the impact of flu vaccine has been harder to determine. Flu comes and goes with the seasons, and often it does not kill people directly, but rather contributes to death by making the body more susceptible to secondary infections like pneumonia or bronchitis. For this reason, researchers studying the impact of flu vaccination typically look at deaths from all causes during flu season, and compare the vaccinated and unvaccinated populations.
Such comparisons have shown a dramatic difference in mortality between these two groups: study after study has found that people who get a flu shot in the fall are about half as likely to die that winter-from any cause-as people who do not. Get your flu shot each year, the literature suggests, and you will dramatically reduce your chance of dying during flu season.
Yet in the view of several vaccine skeptics, this claim is suspicious on its face. Influenza causes only a small minority of all deaths in the U.S., even among senior citizens, and even after adding in the deaths to which flu might have contributed indirectly. When researchers from the National Institute of Allergy and Infectious Diseases included all deaths from illnesses that flu aggravates, like lung disease or chronic heart failure, they found that flu accounts for, at most, 10 percent of winter deaths among the elderly. So how could flu vaccine possibly reduce total deaths by half? . . .
When Lisa Jackson, a physician and senior investigator with the Group Health Research Center, in Seattle, began wondering aloud to colleagues if maybe something was amiss with the estimate of 50 percent mortality reduction for people who get flu vaccine, the response she got sounded more like doctrine than science. "People told me, 'No good can come of [asking] this,'" she says. "'Potentially a lot of bad could happen' for me professionally by raising any criticism that might dissuade people from getting vaccinated, because of course, 'We know that vaccine works.' This was the prevailing wisdom."
Nonetheless, in 2004, Jackson and three colleagues set out to determine whether the mortality difference between the vaccinated and the unvaccinated might be caused by a phenomenon known as the "healthy user effect." . . . Jackson's findings showed that outside of flu season, the baseline risk of death among people who did not get vaccinated was approximately 60 percent higher than among those who did, lending support to the hypothesis that on average, healthy people chose to get the vaccine, while the "frail elderly" didn't or couldn't. In fact, the healthy-user effect explained the entire benefit that other researchers were attributing to flu vaccine, suggesting that the vaccine itself might not reduce mortality at all. Jackson's papers "are beautiful," says Lone Simonsen, who is a professor of global health at George Washington University, in Washington, D.C., and an internationally recognized expert in influenza and vaccine epidemiology. "They are classic studies in epidemiology, they are so carefully done." MORE
While vaccines for, say, whooping cough and polio clearly and dramatically reduced death rates from those diseases, the impact of flu vaccine has been harder to determine. Flu comes and goes with the seasons, and often it does not kill people directly, but rather contributes to death by making the body more susceptible to secondary infections like pneumonia or bronchitis. For this reason, researchers studying the impact of flu vaccination typically look at deaths from all causes during flu season, and compare the vaccinated and unvaccinated populations.
Such comparisons have shown a dramatic difference in mortality between these two groups: study after study has found that people who get a flu shot in the fall are about half as likely to die that winter-from any cause-as people who do not. Get your flu shot each year, the literature suggests, and you will dramatically reduce your chance of dying during flu season.
Yet in the view of several vaccine skeptics, this claim is suspicious on its face. Influenza causes only a small minority of all deaths in the U.S., even among senior citizens, and even after adding in the deaths to which flu might have contributed indirectly. When researchers from the National Institute of Allergy and Infectious Diseases included all deaths from illnesses that flu aggravates, like lung disease or chronic heart failure, they found that flu accounts for, at most, 10 percent of winter deaths among the elderly. So how could flu vaccine possibly reduce total deaths by half? . . .
When Lisa Jackson, a physician and senior investigator with the Group Health Research Center, in Seattle, began wondering aloud to colleagues if maybe something was amiss with the estimate of 50 percent mortality reduction for people who get flu vaccine, the response she got sounded more like doctrine than science. "People told me, 'No good can come of [asking] this,'" she says. "'Potentially a lot of bad could happen' for me professionally by raising any criticism that might dissuade people from getting vaccinated, because of course, 'We know that vaccine works.' This was the prevailing wisdom."
Nonetheless, in 2004, Jackson and three colleagues set out to determine whether the mortality difference between the vaccinated and the unvaccinated might be caused by a phenomenon known as the "healthy user effect." . . . Jackson's findings showed that outside of flu season, the baseline risk of death among people who did not get vaccinated was approximately 60 percent higher than among those who did, lending support to the hypothesis that on average, healthy people chose to get the vaccine, while the "frail elderly" didn't or couldn't. In fact, the healthy-user effect explained the entire benefit that other researchers were attributing to flu vaccine, suggesting that the vaccine itself might not reduce mortality at all. Jackson's papers "are beautiful," says Lone Simonsen, who is a professor of global health at George Washington University, in Washington, D.C., and an internationally recognized expert in influenza and vaccine epidemiology. "They are classic studies in epidemiology, they are so carefully done." MORE
1 Comments:
Actually polio and whooping cough were on the decline when those vaccines were developed, so the claims that those vaccines stopped polio and whooping cough really need to receive the same scrutiny as the flu vaccine just has.
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