How often have you heard some rabidly smug pro-vaccination fanatic proclaim that “vaccines don’t cause autism”? There are several ways that this statement is wrong.

It’s Unscientific

No competent conscientious scientists would ever make the claim that “vaccines don’t cause autism”. They definitely might say that there is no strong evidence that supports a link between vaccines and autism. This is because science is not about proclaiming absolute statements of fact but of supporting explanations with evidence.

Imagine the steps involved in scientifically confirming that “vaccines don’t cause autism”. Every single vaccine currently being used would have to be thoroughly tested using randomized double blind placebo controlled (RDBPC) studies to determine if it could cause autism.

Currently only the MMR vaccine has been tested for links to autism. This does not prove that the MMR cannot cause autism however, it only shows that no link between the MMR and autism has been established yet. The studies may have been deficient in some way such as not looking at the right populations. Perhaps there is only a link between autism and vaccinated children with mitochondrial disease as the Hannah Poling case suggests[1]. No studies have yet looked at whether the MMR is linked to autism in only children with mitochondrial disease.

It’s Illogical

When they say “vaccines don’t cause autism” ask them to support their claim. They’ll say something like “no link has been found” i.e. no hard evidence is there to support a link. So they are saying that the idea that vaccines cause autism is false because there is no evidence to suggest it does. This is an appeal to ignorance fallacy. The appeal to ignorance fallacy occurs when a conclusion is assumed based primarily on lack of evidence to the contrary[2].  “absence of evidence is not evidence of absence.” The appeal to ignorance fallacy is a form of false dichotomy or false dilemma fallacy in that the link between autism and vaccines may not have been studied well. As noted above, only one vaccine has ever been tested for a link between autism and vaccines.

So whenever someone over-confidently proclaims that “vaccines don’t cause autism” know that they are either science illiterate with a poor understanding of basic logic or that they are pretending to be science illiterate in order to further some agenda.

Notes

1. Poling, J. S.; Frye, R. E.; Shoffner, J.; Zimmerman, A. W. (2006). “Developmental regression and mitochondrial dysfunction in a child with autism”. Journal of Child Neurology. 21 (2): 170–172.
2. https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/56/Argument-from-Ignorance.