American Family Physician, the journal of the American Academy of Family Physicians, has a feature called AFP Journal Club, where physicians analyze a journal article that either involves a hot topic affecting family physicians or busts a commonly held medical myth. In the September 15, 2010 issue they discussed “Vaccines and autism: a tale of shifting hypotheses,” by Gerber and Offit, published in Clinical Infectious Diseases in 2009.
The article presented convincing evidence to debunk 3 myths:
- MMR causes autism.
- Thimerosal (mercury) causes autism.
- Simultaneous administration of multiple vaccines overwhelms and weakens the immune system, triggering autism in a susceptible host.
Gerber and Offit reviewed 13 large-scale studies that demonstrated no association between the MMR vaccine and autism. These included ecologic studies, retrospective observational studies and prospective observational studies. The findings were consistent; the only outlier in all the studies of MMR was Dr. Andrew Wakefield’s small, discredited 1998 study, which was fully retracted by The Lancet in early 2010.
They reviewed 7 large-scale studies (again, ecologic, retrospective, and prospective) that consistently demonstrated no association between thimerosal and autism. They showed that the hypothesis was not biologically plausible, since the symptoms of mercury poisoning are distinct from those of autism and are not produced by the thimerosal in vaccines.
They showed that the overload hypothesis is not credible because
- The immunologic load has dropped from 3000 components in the 7 vaccines used in 1980 to less than 200 in the 14 vaccines recommended today.
- An infant’s immune system is capable of handling the thousands of antigens it is exposed to early in life.
- Vaccinated children are not more susceptible to infections.
- Autism is not an autoimmune disease.
The discussants ask “Should we believe this study?” and their answer is a resounding “yes.” They say “This month’s article clearly provides the science and statistics to dispel the theory that childhood vaccinations induce autism. A Cochrane review came to the same conclusion in October 2005.”
They ask “What should the family physician do?” They point to evidence that information and assurance provided by health care professionals can make a difference. They even suggest that physicians get a copy of the Gerber/Offit article and keep it handy for when parents are apprehensive about immunizing their child.
The Journal Club doctors evaluated the evidence rationally and accepted the logical conclusions. The anti-vaccine activists didn’t: instead, they have endangered our public health by rejecting or postponing immunizations and repeating myths. Shame on them!
This article was originally published in the Science-Based Medicine Blog