From what I've read on autism sites, most of those kids have leaky gut syndrome and many improve when casein and gluten is removed from their diet. I don't think autism is a simple one cause thing. From what I've read on the kids that have dramatic improvements they've undergone mercury removal, dietary changes as well as addressed nutritional deficiencies and undergone cognitive therapy.
A lot of these kids have super sensitive nervous systems and the nurtoxins in the vaccines and the inability to handle casein and gluten probably sent them over the edge.