My oldest daughter is autistic and I'm pretty sure I know why. Autism spectrum disorder has a huge genetic component and is linked to families with high intelligence, which makes sense since they recently discovered that an autistic brain has too many neuronal connections.
Leila had birth complications, but despite our worries she was advanced in almost everything. She delighted in freaking people out by waving and saying "hi!" to them at six months. She discovered at a very early age that she could roll anywhere she wanted to go, so had no need to learn how to crawl. She walked at a normal age, and it only took a single day to potty-train her at fifteen months.
Then she got her MRI when she was two. An hour or two after we got home she started crying, then screaming and running a fever; we had no thermometer so don't know how high. We called the doctor, who said it wasn't that unusual and not to worry.
By the next morning she stopped talking, stopped using the potty, stopped playing, and withdrew into her own little world. Note this was early 1988 before vaccine fears came about and before autism was well known. Despite our poverty we took her to specialists, every one of whom misdiagnosed her. One doctor said mentally retarded, one checked her hearing and said she was deaf and we should all learn sign language (Leila has better ears than anyone I know).
It's my belief that a very small number of children who have the genetic component can't handle getting all three vaccines at once, or perhaps is allergic to some component. The doctor said fever is common, but perhaps a dangerously high fever happnes, too. That's what I think caused Leila's problems.
At any rate, thanks to the incompetence of some highly educated quacks, Leila, who turns 30 this year, will never hold a job or drive a car. She spends most of her time reading the news on the internet; she has the worst interpersonal skills of anyone I ever met.
You can be sure that we got separate vaccinations for Patty, rather than the MMR superbomb.
Get the measles vaccine, NOT the MMR. Get the shots separately, and if your kid gets a fever afterwards, take him or her to the hospital. We're a lot less ignorant than we were when Leila was 2 or 3.