The Healthy User Effect
Another study conducted in Canada, (unmentioned by the CDC) found that taking the flu shot gave you a 51 percent reduced odds of death if you were hospitalized with pneumonia. Why wasn’t this publicized, since it’s such a dramatic reduction?
Dr. Doshi explains that this Canadian study had an unusual aspect; it focused on patients outside the flu season…“when it is hard to imagine the vaccine could bring any benefit. And the authors, academics from Alberta, Canada, knew this: the purpose of the study was to demonstrate that the fantastic benefit they expected to and did find—and that others have found, such as the two studies that CDC cites—is simply implausible, and likely the product of the “healthy-user effect”
The ‘healthy user effect’ explains that healthy people are more likely to be vaccinated than less healthy people and as a side effect of being healthy and potentially more careful, are less likely to suffer death or illness. According to Dr. Doshi, “Healthy user bias threatens to render the observational studies, on which officials’ scientific case rests, not credible.” Dr. Doshi goes onto explain that for many people, hearing that vaccines save lives, means that there has been substantial evidence behind that statement. However, the CDC national guidelines states,
“. . . studies demonstrating large reductions in hospitalizations and deaths among the vaccinated elderly have been conducted using medical record databases and have not measured reductions in laboratory-confirmed influenza illness. These studies have been challenged because of concerns that they have not controlled adequately for differences in the propensity for healthier persons to be more likely than less healthy persons to receive vaccination.”
There has only been one randomized trial of influenza in the elderly conducted twenty years ago and it showed no mortality benefit. This means that the influenza vaccine is targeted to a group of people without any clinical trials showing its benefit.
So is there any good news for the influenza vaccine? There have been many randomized control trials of influenza vaccines in the healthy adult population. And depending on how well the vaccine strains matched up with the circulating strains, vaccinating between 33 and 100 people resulted in one less case of influenza. However, these studies were on the healthy population, not on specific populations such as the elderly or pregnant women.
To make things worse, this past influenza season, Australia stopped vaccinating children under the age of five due to safety concerns with the influenza vaccine. Apparently, 1 in every 110 vaccinated children were having febrile seizures after vaccination. In Sweden and Finland, H1N1 vaccinations in 2009 were associated with an increase in narcolepsy cases in adolescents ( 1 in every 55,000 vaccinated adolescents).
Questions and Answers with Dr. Doshi
Decoded Science had the opportunity to interview Dr. Doshi about his study. He cautions that we should stop calling the influenza vaccine a ‘flu shot,’ saying, “They are not vaccines against “flu” but against”influenza” and the two are not the same. Please see my article (towards the very end) for more details on this.”
Decoded Science: What made you decide to investigate what is really behind the flu shot?
Dr. Doshi: “I have a long standing interest in the intersection of science and policy. My interest in influenza goes back to around 2004.”
Decoded Science: What is your recommendation to medical and public health experts, as well as the everyday person reading this? Should we continue to get the flu shot? Do you think there are certain groups that should get the flu shot? What about parents who are trying to decide for their children?
“Public health experts are routinely misleading the public as to the strength of the science in support of its statements about vaccine effectiveness, safety, and the threat of influenza. For public health to function properly, it needs to gain the trust of the public and accurate information is an obvious prerequisite for that trust. My recommendation to public health experts is to inform the public about the limitations in the expected potential benefit of influenza vaccine. Most flu is not influenza, and marketing influenza vaccine as a “flu shot” misleads the public into holding overoptimistic views of vaccine benefit. No we should not continue “business as usual”. The vaccine is not always “better than nothing” — see the BMJ article and this article. Rather than saying who “should” do this and that, we need to do our own homework on this topic.”
Decoded Science: Could you comment on the studies that show that getting the flu shot may not prevent you from getting sick, but can help prevent you from getting a serious case?
Dr. Doshi: “This the most important issue, as uncomplicated cases of influenza do rise in severity to the level of a public health problem. It is complications that can result that make it of relevance to public health. My paper addresses the studies that claim influenza vaccines reduce the risk of influenza complications. No good studies support this claim.”
Any final thoughts or comments?
“I would encourage you to take specific questions to the CDC regarding its policy.”
Flu Shot vs. Influenza Vaccine
So what do you do when you’ve always been told by the experts to get your influenza vaccine every year? As Dr. Doshi says, we should do our homework. This paper highlights how looking at the big picture, and not just what you want to see, brings to light a whole new perspective. Be your own detective, read the studies, ask questions, and be proactive about your health.
Doshi, P. Influenza: marketing vaccine by marketing disease. British Medical Journal. May 16, 2013. Accessed May 16, 2013.
CDC. 2012-2013 Seasonal Influenza Vaccine Safety. (2013). Accessed May 16, 2013.
CDC. Recommendations of the Advisory Committee on Immunization Practices (ACIP). (2008). Accessed May 16, 2013.
Doshi, P. Are US flu death figures more PR than science? (2005). BMJ. Accessed May 16, 2013.
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