For the record: I don't know.
I do think it is likely multi-factoral with many variables influencing risk of developing autism (with some more heavily weighted than others).
I also think it is unspeakably arrogant to dismiss vaccines as a variable, especially because the kind of study that would, with greater certainty, identify if vaccines are (or are not) a variable has not been done - namely, a long-term study comparing the health of a group of vaccinated people compared the health of a group of unvaccinated people (with unvaccinated defined as not having received any vaccines of any kind - not simply not receiving whatever vaccine is being studied).
An prospective observational study would be a start, but ultimately it will be necessary to do a randomized, controlled, double-blind study comparing vaccinated with unvaccinated children. The real challenge would be finding a group of parents who are pro-vaccine but also willing to forgoe them if they randomized to the no vaccine group. There would be no point in approaching those who are "vaccine hesitant" because the vast majority who are in this group got there due to previous negative experience with "coincidence" (aka: a bad experience with vaccination - the adverse events that the pro-vaccine crowd loves to dismiss as never happening).
There are a multitude of studies touted as "proving" vaccines do not cause harm - yet when one looks at the methods of those studies you see the common problem with study design
that limits (or prevents) such studies from proving vaccines are, or are not, a potential variable in a variety of acute and chronic health issues. And there in lies the problem - those who love vaccines interpret such studies with rose-colored lenses while those who are "vaccine hesitant" have a far different analysis of these same studies. Oddly enough, "pay to play" comes to mind as it seems so many of those who advocate for vaccines can be rightly accused of conflict of interest as they benefit financially through said advocacy while those who are more critical of vaccines generally do not benefit financially from them.
Financial carrots and sticks are now increasingly used as a way to control both patients and providers - and vaccine status is a variable in this calculus.
Medicine has a long history of barging ahead with a minimum of information (aka: evidence) and ultimately pulling back as additional information came to light (just in obstetrics: overuse of episiotomy, "once a cesarean section, always a cesarean section", there are a multitude of other examples in other specialities). And this pattern continues unabated. It is my opinion, and my hope, that we will soon recognize this is true of vaccines as well.
Vaccinosis is recognized in animal medicine. The list of symptoms is shockingly similar to the types of adverse events (aka: "coincidences") people report following vaccination in humans. This kind of cognitive dissonence serves no one and certainly does not help any individual or group achieve better health.
Because we do not have adequate safety studies for vaccines we cannot rationally evaluate if they do more good than harm. It is possible there is benefit to contacting the diseases for which we now vaccinate - because the odds of recovery are (generally) good and the likelihood of permanent harm is low, while the cost of vaccinating (fiscally - because this must be done repeatedly to maintain suppression of disease) may be much higher than previously calculated. Yes - it costs money when someone is sick (in lost work and/or in seeking medical care during the illness) - yet if getting sick once results in robust life-long immunity the one time cost must be weighed against the cost of continuously vaccinating throughout a persons lifetime to maintain suppression of disease while also calculating the financial cost of any adverse effects of vaccination (once we have more reliable information about this because we have looked at the long-term health comparing vaccinated and unvaccinated).