Archive for August 24th, 2009

The perils and pitfalls of doing a “vaccinated versus unvaccinated” study

The anti-vaccine movement is nothing if not plastic. It “evolves” very rapidly in response to selective pressures applied to it in the form of science refuting its key beliefs. For instance, when multiple studies looking at the MMR vaccine and autism failed to confirm the myth that the MMR causes autism or “autistic enterocolitis,” most recently late last year, it was not a problem to the anti-vaccine movement. Neither was it a major problem to the movement when multiple studies similarly failed to find a link between mercury in the preservative thimerosal that used to be in most childhood vaccines and is no more (except the flu vaccine) and autism. No problem! Andrew Wakefield is alleged, based on strong evidence, to have falsified his data alleging a link between the MMR vaccine and “autistic enterocolitis”? Fuggedabouddit! The anti-vaccine movement simply pivoted neatly, de-emphasized points that the evidence was so clearly against that even they couldn’t spin it to a positive anymore, and found new bogeymen. These days, it’s the “toxins” (such as formaldehyde and the latest antivax bogeyman, squalene), and “too many too soon” (a gambit given seeming respectability by Dr. Bob Sears and Dr. Jay Gordon, apologists for and supplicants to the anti-vaccine movement both.

However, there is one trait of the anti-vaccine movement that, however its camouflaging plumage may evolve, never, ever changes. It is as immutable as believers say that God is. That trait is that, whatever other claims, the anti-vaccine movement makes, at its core it is always about the vaccines. Always. No matter how often science fails to find a link between vaccines and autism or vaccines and whatever other horreur du jour the anti-vaccine movement tries to pin on vaccines, no matter how many studies do not support the viewpoint that vaccines cause autism, no matter how much the anti-vaccine movement tries to deny and obfuscate by saying that it is not “anti-vaccine” but rather “pro-safe vaccine,” at its core the anti-vaccine movement is about fear and loathing of vaccines. Always. When inconvenient science doesn’t support their views, anti-vaccine activists either ignore the science, distort the science, or launch ad hominems against the people doing the science or citing the science. And, as I said before, the claims of the anti-vaccine movement evolve. Never again will the anti-vaccine movement make the horrific mistake of yoking itself to a hypothesis that is as easily testable as the hypothesis that mercury in vaccines causes autism. The claim that mercury in vaccines causes autism predicted that, if thimerosal were removed from vaccines or reduced to pre-”epidemic levels” of the early 1990s, then autism rates should plummet. Thimerosal was removed from nearly all childhood vaccines (the sole exception being some flu vaccines), reducing infant mercury exposure from vaccines to levels not seen since the 1980s; yet autism rates continue to rise. This is about as resounding a refutation of the hypothesis that mercury in vaccines is a major cause or contributor to autism that even the anti-vaccine movement has backed away from the pure claim, which has now evolved to unnamed “environmental toxins,” either in concert with mercury or with other nasty things, as being the Real One True Cause of Autism.

It’s evolution in action. These new claims are much “fitter” because they are much harder to falsify through scientific research, epidemiology, and clinical trials.

Posted in: Clinical Trials, Medical Ethics, Public Health, Science and Medicine, Vaccines

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