MMR Vaccine and Autism

From SkepticWiki

1 Definitions
2 Claim that the MMR vaccine can cause Autism
3 Problems with the Claim
4 Related Topics
5 References

[edit] Definitions

Autism, also known as autistic spectrum disorder, is a developmental disability that affects the ability to communicate and socialize.

The MMR vaccine is a combined vaccination, given by injection, for measles, mumps, and rubella. Like most vaccines, it contains inert versions of the same or similar viruses which cause the body to produce antibodies capable of fighting the real viruses should it ever become infected with one.

[edit] Claim that the MMR vaccine can cause Autism

The initial source for the claim is Dr. Andrew Wakefield of the Royalty Free Hospital in London. He and twelve of his colleages published in the medical journal The Lancet in 1998 that there was a link between children who had received the MMR vaccine and children with late-onset autism. This claim appears to be supported by the fact that the number of children diagnosed with autism (in proportion to the child population) has risen steadily since the introduction of the MMR vaccine in 1988.

[edit] Problems with the Claim

The link between MMR and autism was tenuous at best. Wakefield et al claimed that the MMR vaccine resulted in bowel problems, which led to a decreased absorption of vitamins and nutrients, and that this led to the autism. However, even if the link between the bowel problems and nutritional deficiencies holds, there has never been any evidence of any nutrition-based cause for autism, and Wakefield et al provided no scientific analysis to substantiate this.

Another problem with the Wakefield study was that it was based on only twelve cases. This is too small to be statistically reliable. Also, in four of the twelve cases, the symptoms of autism showed up before the symptoms of bowel disease.

Other studies performed by other researchers have failed to replicate the effect. In fact, the next year, The Lancet published a paper refuting the link between MMR and autism; many others have followed.

While it is true that the number of cases of autism has been growing, the fact is this growth started around 1979 and is probably due to a greater awareness of the issue, leading to more cases being diagnosed that would have been missed before. There was no jump in the rate with the introduction of the MMR vaccine in 1988.

The point at which autism is diagnosed is different than the point at which it began. Studies show that autism can be traced back to at least a prenatal origin. Some studies support a genetic cause.

It has been discovered that Wakefield and the Royal Free Hospital had patents for a number of vaccines and other products that would stand to profit if the MMR vaccine was discontinued. Wakefield is now also selling many claimed treatments for autism, none of which have been scientifically shown to have any positive effect.