You know, I don't really think that the anti-vaxx people disbelieve in vaccines' efficacy. The scary thing about them is that they'd rather their baby having a chance of being dead than a chance of being autistic.
I truly believe that (and knowledge of how fascism works) is the reason so many adults don't get bother to get an official autism diagnosis. There's a real sense that society doesn't want you around. If you don't have physical comorbidities like EDS that need treatment, it's all pain, no gain.