Statistically, there has been a significant jump in the number of children being diagnosed with autism since the MMR vaccination was introduced. There is still debate over exactly what the cause of that is.

The pro-immunisation lobby believe that this jump in numbers is a result of the condition becoming more commonly recognised, understood, and diagnosed, especially now that we consider it an autistic spectrum disorder - ie. something that can have a range of effects, from mild to severe.

The anti-immunisation lobby believe that the timing is too close to be a coincidence (such a sudden and significant increase in diagnosis, right at when the MMR was introduced) and that there are other factors which make it likely that the increased incidence of autism is related to the MMR. As well as this, up to 2001-2002, the MME vaccines contained thimerosal, which contains mercury, in an attempt to cause a heightened immune reaction to the vaccination; the symptoms of mercury poisoning are very similar to autism.