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Autism and Vaccines? Correlation is not Causation

One of the most deeply controversial claims in regards to the cause of Autism is where it is assumed that MMR vaccinations cause ASD.

A paper published in 1998 by Andrew Wakefield and co-authors claimed there was a connection between ASD and MMR. It was based on a sample of 12 children who were admitted for gastrointestinal issues at a hospital in London. The study claimed that the initial symptoms of ASD appeared in all children within 2 weeks of getting vaccinated along with a combination of inflammatory bowel diseases. If true this claim holds big moral implications. The temporal connection of diagnosis and injection was enough to spawn a massive and uninformed Anti-Vaccine movement. Why is this study so controversial then?

After several years of vigorous investigation, Brian Deer, an investigative journalist, put together an extensive report that ultimately stripped Wakefield of his medical licence. Deer found many flaws and misleading assumptions surrounding the study. He exposed Wakefield’s connection with a law firm intent on suing MMR vaccine manufacturers. The law firm funded his scientific investigation, questioning his motives for the study. An extract from Deer’s original website explains the transaction in more detail:

“Barr [the lawyer] paid the doctor with money from the UK legal aid fund: run by the government to give poorer people access to justice. Wakefield charged at the extraordinary rate of £150 an hour …These hourly fees – revealed in The Sunday Times in December 2006 – gave the doctor a direct personal, but undeclared, financial interest in his research claims: totalling more than eight times his reported annual salary and creating an incentive not only for him to launch the alarm, but to keep it going for as long as possible.”

http://briandeer.com/mmr/lancet-summary.htm

Additionally, Deer hunted down the families of the 12 children from the study and realised that the parents fell prey to false memories and altered evidence. The children were hired through Anti-MMR campaigners and their parents were allegedly contacts with Barr himself. When interviewing these parents he found that they had already noticed abnormal symptoms prior to the vaccination and some children didn’t have Autistic symptoms a few months after the investigation after all. To top it off, even with bigger sample sizes, consequent studies were unable to replicate the results of Wakefield’s original study.

As a result of this study, of which news spread widely through UK and US, a number of parents stopped having their children vaccinated in fear of their kids becoming Autistic. Consequently, in 2013 a large incidence of measles broke out in Swansea, Wales. About 1,200 cases were reported including one death. It was noted that parents refused immunisation and a common reason was that they were worried about the link with Autism. It comes as no surprise as after the paper was published more than 10 years ago, MMR immunisations fell from 94% to 67.5% in Swansea. 

Desperate parents are eager to find the cause of any abnormalities seen in their kids, and who can blame them. Because Autism is usually diagnosed around the time the MMR injection is given at about 2 years old (first dose), it is easy to see why they would match two and two together. Even mum believed this at first, although Chris was diagnosed later at 4. She already knew he was different the day he was born but that didn’t stop her from almost believing their could be a connection to the vaccines. To add to the complication, the prevalence of ASD around the world has shown huge increases. In the 1970s (also around the time the MMR vaccine was introduced), an estimated1 in 2000 were diagnosed with ASD and now it is 1 in 100. Census figures in UK state a 1.1% prevalence rate. Has the MMR injections increased the prevalence of Autism?

Over the years, diagnosis for Autism has broadened to include more behavioural traits as seen in Autism Diagnostic and Observation Schedule (ADOS) and other diagnostic methods. The DSM-V now includes Aspergers in the Autism Spectrum. This broader diagnosis would inevitably show increased prevalence as more individuals are identified with the symptoms. Therefore, we can’t assume that increased prevalence means increased incidence. As Autism is on a spectrum of behaviours, it is likely that the incidence rate has remained the same throughout global populations. I’ve added a bell curve below to demonstrate this. 

Bell Curve to show how a more inclusive diagnosis can cause higher prevalence.

Bell curve to show how a more inclusive diagnosis can cause higher prevalence.

Getting the right information out their can mean life or death, please vaccinate your kids.

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