The most common sentence from scientists or about science I have found in news articles about the autism-vaccine connection goes like this:
"Studies repeatedly discount any link between thimersol (or MMR or vaccines) and autism."
This is generally right. The overall scientific evidence has not demonstrated that there is a connection between vaccines (or any component of vaccines) and autism. Yet clearly this has not stopped the debate or convinced most parents of children with autism.
So I keep asking, why not? In part, this hypothesis is kept alive by a variety of people who are effectively using the media to focus on this issue.
But I also think that scientists have not engaged in the pubic debate effectively by providing the evidence for why this in not the case. We keep repeating the conclusions as if when "experts" (at least from the scientific community) speak that is the final word. On the other hand, parents of autistic children, another kind of "expert" continue to voice their views that their personal experience is otherwise. That is, there is a connection between the timing of their children's vaccine and the onset of autistic symptoms.
Scientists must find a way to talk about the lack of convincing evidence for a vaccine to autism link, yet validate parents' experiences that there seems to be a relationship. Tough assignment, but necessary.
Scientists will be much more convincing in the long-run if they acknowledge the importance of generating various hypotheses (like vaccines as a cause) and the careful exploration of these hypotheses and the often mixed evidence that emerges.