Do vaccines cause autism?
If you are remotely connected to autism, it is highly likely you have come across this question before. The answer is, no, vaccines do not cause autism. This theory was proposed in 1998, has been thoroughly investigated and conclusively proven to be false by 2010. What contributes to its widespread popularity and longevity?
Origin of the vaccine connection
In 1998, a physician by the name Andrew Wakefield made this claim in a paper published in the medical journal Lancet. During that time, the two most popular candidates for the cause of autism were refrigerator parenting and genetics/neurobiology. Wakefield looked at 12 children who were developing normally until the administration of the Measles, Mumps, and Rubella (MMR) vaccine and started exhibiting autistic symptoms shortly after. He believed that the vaccine affected the large intestine and assumed that neurotoxic proteins released through the intestine reached the bloodstream and brain, causing autism. His belief was strengthened when all the children he performed colonoscopies on exhibited the lesions.
The theory made sense as autism symptoms in children started to appear around the same time as the vaccine administration i.e. 12 to15 months of age. “It was after the vaccine that my child stopped talking/ started behaving this way” is a common refrain one hears even today. The theory also gained popularity with parents as it took away the burden of blame from them. Autism cases were increasing rapidly, people were looking for a cause, and this plausible theory gained credence.
Debunking the theory
The vaccine link looked obvious and was convenient but other researchers were unable to replicate the findings. Also, considering the diversity of how autism presents itself, a common biological cause looked unlikely to the scientists. In 2005, an investigative reporter alerted the editors at Lancet that Wakefield's study had been flawed by severe research misconduct, conflict of interests, and falsehood.
After investigating the matter, Lancet retracted the article, and the British Medical Association took disciplinary actions against Wakefield. Since then, any direct connection between autism and the MMR vaccine has been discredited by dozens of studies investigating the roots of autism and the biological effects of MMR and the mumps virus. Also, even as more parents were opting out of MMR vaccination, the rates of autism had been rising.
Soon after, there was a suspicion about another autism-vaccine link. It was suspected that thimerosal, added to vaccines as a preservative, could cause autism. Thimerosal contains mercury, a poison, but there was no evidence that the small amount was harmful. To see if thimerosal was linked to autism, researchers studied children who received vaccines that contained it. They compared them to kids who received vaccines that did not contain thimerosal and did not find significant differences in the rates of autism. Even then, thimerosal was taken out of most vaccines.
::: {.callout-note appearance="minimal"} Since 2003, there have been nine studies funded or conducted by CDC (Center for Disease Control) that have found no link between thimerosal-containing vaccines and ASD (autism spectrum disorder). These studies also found no link between the MMR vaccine and ASD in children. :::
Researchers have also looked to see if all the vaccines required before age 2 together somehow triggered autism. Children receive 25 shots in the first 15 months of life. Some people feared that getting all those shots so early in life could lead to the development of autism but there is no evidence that this is true. The CDC compared groups of children who received vaccines on the recommended schedule and those whose vaccines were delayed or did not get them at all. There was no difference in the autism rate between these groups.
Thus, through these several scientific studies, it has been concluded that there is no evident link between vaccines and autism.