The Uncertain Science of Flu Vaccines

flu_strategiesThe November 2009 edition of the Atlantic Monthly contains an important article, “Does the Vaccine Matter?”  by Shannon Brownlee and  Jeanne Lenzer. The authors — after acknowledging the dramatic success of vaccines for diseases such as whooping cough and polio — focus on the unique difficulty of scientifically establishing the effectiveness of vaccines against the ever-evolving flu.

They also acknowledge that “it’s only a matter of time before we’re hit by a truly devastating flu pandemic — one that might kill more people worldwide than have died of the plague and AIDS combined.”

Brownlee and Lenzer are concerned strictly with science, not with conspiracy theories about corporate plots to invent fictional pandemics in order to panic the public into buying unneeded vaccines, or plots by the government to kill off masses of American people.

They find, however, that — considered scientifically —  the effectiveness of flu vaccines is not well established.

And they report the views of contrarian flu experts who worry that by having over-confidence in flu vaccines of doubtful effectiveness, we may be passing up the chance to do placebo studies to establish their true effectiveness. And we may also be overlooking other, more ordinary strategies for protecting ourselves against the world-ravaging flu pandemic yet to come.

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? Tom Jefferson, a physician based in Rome and the head of the Vaccines Field at the Cochrane Collaboration, a highly respected international network of researchers who appraise medical evidence, says: “For a vaccine to reduce mortality by 50 percent and up to 90 percent in some studies means it has to prevent deaths not just from influenza, but also from falls, fires, heart disease, strokes, and car accidents. That’s not a vaccine, that’s a miracle.”

Here’s the sort of reasoning that raises doubts about the flu vaccine:

Lisa 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.” They hypothesized that on average, people who get vaccinated are simply healthier than those who don’t, and thus less liable to die over the short term. People who don’t get vaccinated may be bedridden or otherwise too sick to go get a shot. They may also be more likely to succumb to flu or any other illness, because they are generally older and sicker. To test their thesis, Jackson and her colleagues combed through eight years of medical data on more than 72,000 people 65 and older. They looked at who got flu shots and who didn’t. Then they examined which group’s members were more likely to die of any cause when it was not flu season.

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.”


The history of flu vaccination suggests other reasons to doubt claims that it dramatically reduces mortality. In 2004, for example, vaccine production fell behind, causing a 40 percent drop in immunization rates. Yet mortality did not rise. In addition, vaccine “mismatches” occurred in 1968 and 1997: in both years, the vaccine that had been produced in the summer protected against one set of viruses, but come winter, a different set was circulating. In effect, nobody was vaccinated. Yet death rates from all causes, including flu and the various illnesses it can exacerbate, did not budge. Sumit Majumdar, a physician and researcher at the University of Alberta, in Canada, offers another historical observation: rising rates of vaccination of the elderly over the past two decades have not coincided with a lower overall mortality rate. In 1989, only 15 percent of people over age 65 in the U.S. and Canada were vaccinated against flu. Today, more than 65 percent are immunized. Yet death rates among the elderly during flu season have increased rather than decreased.

Finally, the authors summarize the kinds of strategies which are well-known to reduce the risks of getting the flu:

“Launched early enough and continued long enough, social distancing can blunt the impact of a pandemic,” says Howard Markel, a pediatrician and historian of medicine at the University of Michigan. Washing hands diligently, avoiding public places during an outbreak, and having a supply of canned goods and water on hand are sound defenses, he says. Such steps could be highly effective in helping to slow the spread of the virus. In Mexico, for instance, where the first swine flu cases were identified in March, the government launched an aggressive program to get people to wash their hands and exhorted those who were sick to stay home and effectively quarantine themselves. In the United Kingdom, the national health department is promoting a “buddy” program, encouraging citizens to find a friend or neighbor willing to deliver food and medicine so people who fall ill can stay home.

They conclude:

The safety of the swine flu vaccine remains to be seen. In the absence of better evidence, vaccines and antivirals must be viewed as only partial and uncertain defenses against the flu. And they may be mere talismans. By being afraid to do the proper studies now, we may be condemning ourselves to using treatments based on illusion and faith rather than sound science.

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