The research looking for a link between autism and vaccination has already been done, (and is probably still being done). Huge studies, looking at, for example, all 500,000+ children born in Denmark between 1991 and 1998, have not found any such link. Stopping giving MMR vaccines in Japan has not decreased the rate of increase of autism there. And so on: there have been many studies made of this stuff. If there were a link, no matter how obscure or how weird the actual causality was, these studies would pick it up.

I know it's hard to understand, or hard to believe, when you have a child who reacted badly to a vaccine and was then diagnosed with autism. But life is full of weird coincidences that are just that: coincidence. That's why we use large scale studies, to figure out the coincidences from the things that are actually causal and not coincidence at all.