The first theory concerning vaccines and autism involved the MMR vaccine. This theory was popularized by the media in the United Kingdom and still is believed by a significant minority of the population. In response to this theory, MMR vaccination rates have dropped below 50% in some communities, causing a resurgence of measles and mumps. Those who believe in this theory in the UK are often utterly convinced it has caused the autism ‘epidemic’.

Sound familiar? The MMR equivalent in the United States is thimerosal. Those who believe thimerosal causes autism in the US are just as fervent as those who think autism is caused by the MMR vaccine in the UK. And, the theories leak across geographic boundaries. The MMR hypothesis is becoming increasingly popular in the US as the evidence against thimerosal has reached such profound levels despite extremely strong evidence likewise against the MMR theory.

The logical problem that exists here is that it is largely impossible for both theories of autism to be correct. The theories have very different mechanisms of action. The thimerosal theory says autism is caused by vaccines because of the action of mercury which causes neurodevelopmental degradation in the brain. The MMR Theory says vaccines cause autism (I am not quite sure there is a unified theory, but at least according to Andrew Wakefield the original purveyor of this theory) through a complicated interaction between the measles virus (causing a leaky gut which allows partially digested proteins to escape the intestines and cause abnormalities in the brain), the gut, and the brain. It would very hard to imagine that both of these theories can be true, that both are dominant causes of autism when there are so many other possible contributors that don’t involve vaccines. But, if they can’t both be true, which one is wrong? Both theories are fervently supported by thousands of parents and others who KNOW them to be true. Both have tens of thousands of supporters who would violently refute a claim their theory is incorrect. So, which one is true and which one is not? The best answer is that both are wrong. Both have in fact been thoroughly scientifically disproved by literally dozens of scientific studies.