‘Tis the Season: Why Not To Get A Flu Shot

As we head into flu season and are deluged with media messages, shopping discounts, pressure from physicians, films exploiting our fear of deadly infectious diseases, pressure from employers and the multibillion dollar flu vaccine marketing machinery, it is a good time to examine the scientific evidence behind flu vaccine safety and effectiveness.

An article in the Journal of Clinical Epidemiology (JCE) points out that the influenza vaccine may be less effective than it is marketed to seem. For one, it’s impossible to determine the incidence of influenza at any time due to the clinical similarity between influenza (caused by influenza A and B) and influenza-like illness (which is caused by around 200 microorganisms, some of which remain unknown). Since these two diseases are clinically indistinguishable, nobody knows how many cases of influenza-like illness in any given year are actually caused by influenza viruses. Similarly, nobody knows the precise death rate caused by influenza, because there is no system of routine autopsies to identify the microbiological cause of death. In other words, deaths that we think may be caused by influenza may actually be caused by influenza-like illnesses instead, which the flu vaccine would not have prevented at all.

Another major factor undermining our understanding of the effectiveness of the flu vaccine is the unreliability of medical studies. We have posted on this subject before, and the JCE article underscores this point:

Cochrane and other systematic reviews have shown overall poor quality methods of relevant studies, a lack of randomized controlled trials of sufficient duration, and power to detect an effect on serious outcomes (such as hospitalization and death) and over-reliance on nonrandomized studies

All these problems mean that the data we do have is simply confusing. For children under two, there is no evidence that the vaccine has any effect at all – the data is similar to that for a placebo. Meanwhile, in older children and adults, better quality randomized studies show some effect against cases of the flu, but none against its complications or transmission. In people over 65, the data makes almost no sense, showing that the vaccine is apparently effective for the prevention of nonspecific outcomes, but does not prevent influenza or influenza-related death. This could be because of the type of data collected – particularly in the general elderly population, most data comes from poor quality, large, retrospective studies that were actually researching something other than influenza. Generalizing from these large pools of data becomes particularly difficult, since, because the studies themselves had a different focus, the information required to study influenza is not always recorded.

These findings were upheld by a study in the British Medical Journal which examined the relationship between study concordance, their take-home message, funding, and the number of times they were cited in comparative studies on the influenza vaccine. The researchers found that better quality studies (which appeared to have less risk of being biased in any direction) were more likely to be in agreement, and were also more likely to conclude that the influenza vaccine was not effective.

Given all this data, one can only conclude that the benefits of the influenza vaccine can only be very slight, if the vaccine works at all, and the massive amounts of money expended every year on vaccination programs suddenly fail to be justifiable.

Policymakers, however, seem to believe differently. The JCE article looked at policy documents on influenza vaccination from the World Health Organization (WHO) as well as five first world countries including the U.S., Canada, and the U.K. However, few of these actually cited the scientific evidence behind their claims, and none contained methodological quality assessments of the studies they relied upon. Moreover, only one document listed conflicts of interest on the parts of the authors. Some did not even explain the methodology used in creating the policy, while the systemic reviews on which they relied upon in creating the policy are often outdated or incorrectly cited. As the JCE article concludes:

Such startling findings make us wonder why the issue of scientific evidence is not taken seriously by policy-makers at such high levels … We wonder whether policymakers seriously intend reducing the burden of acute respiratory infections. If they do, we have effective, acceptable, and cheap interventions (such as handwashing, distancing, and mask wearing) which could be used all together in periods of danger.

The BMJ researchers go some way towards explaining why, if the vaccine is not effective, it is still so popular. Their study found that studies funded by the pharmaceutical industry were far more likely to conclude that the vaccine was effective. These same studies were also far more likely to be published in prestigious journals:

Those [studies] sponsored by industry had greater visibility as they were more likely to be published by high impact factor journals and were likely to be given higher prominence by the international scientific and lay media, despite their apparent equivalent methodological quality and size compared with studies with other funders.

The article adds that these findings “might help to explain the continuation of a near global policy [regarding influenza vaccination], despite growing doubts as to its scientific basis.”

Our pharmaceutical industry is clearly more obsessed with profits than with our health. Investing in research that supports their product’s safety and effectiveness is simply a good marketing ploy as far as they are concerned. But what of our policy-makers? Do they just not do the research? Or, like Rick Perry, are they are content to be bought off with a share of the profits? Whatever the reason, it seems clear that the drive towards vaccination will not end anytime soon… even though the scientific evidence is against it.

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