I have known some Amish. Perhaps it wasn't autism, but I've seen several "special needs" Amish children.
the Amish have a genetic problem that causes mild retardation and a malformation of the heart. For that reason they often send their children to other Amish settlements in Ohio etc to find husbands and wives.
But these children are retarded, and often cared for in the Amish community...
As for Autism, it is not the same, although it overlaps with retardation...many children diagnosed as retarded or as "childhood schizophrenia" in the 1950's would now be called autistic...but back then, they were placed in "homes" for care...
I had one autistic/moderately retarded Amish child in my care...and two others profoundly retarded but not really "autistic" from Mennonite or Amish homes...
Alas, retardation is not PC, so now children with brain damage and severe behavior problems who would be called retarded or as having "childhood schizophrenia" in the past are now called "autistic"...
The trouble with anecdotes is that these people often don't see parents who cared for such children at home in the past...
That is because they live in such close knit communities, they intermarry.
"but I've seen several "special needs" Amish children."
Yes, that's because the inbreeding diseases are rampant. Rampant enough even to hide autism?
Interesting comment. Reminds me of my Soviet expatriate colleague (no defender of communism, believe me) who nonetheless said the old Soviet Union didn't have cases of mental illness, and attributed it to there being less stress in society.
Upon further discussion, however, I concluded that the communist system just covered up such instances of mental illness very effectively. That is, you wouldn't get fired even if you did a lousy job at work (or even failed to show up), and so the mental cases just continued to draw checks, failed to perform, but were pushed along by the system.
I don't know what to make of the autism/vaccination connection, but I agree with several posters that correlation is not the same as causality.