Sigh... there is also a correlation between the increase in autism and the decrease in pirates, but I don't think anyone is suggesting we need more pirates, or that is something we should fund for causation. The vaccine link has been studied, and aside from the study that was discredited because the data was made up, zero causation has been found.
Autism itself is diagnosed by psychologists, not by any kind of repeatable medical marker, and the definition keeps expanding to include all kinds of things that previously were separate diagnoses all together (like Aspergers for example). If you go back a few generations in history, people were just considered weird or massively disabled and there was no diagnoses, but there is lots of evidence with all kinds of people having autistic traits throughout history.
So the rate itself will increase simply on the basis of the widened net of the diagnoses and increased screening, plus actual understanding of the conditions. Additionally, people diagnosed as adults in their 40s, 50s and 60s didn't suddenly wake up with it, so getting a relevant incidence rate would have to involve adjusting the date backwards to a standard reference point (ie birth date) instead of a diagnosis date.
All the current research indicates it's a genetic condition that you are born with, with some possibilities that there are general environmental conditions for in vitro exposure that may aggravate the development of it if you are someone who is predisposed towards it, but things are basically locked in before you are born. There are a lot of different conditions (generically lumped in under 'neurodiversity') in the same boat, and lots of people in and out of the CAF leading productive lives with no issue.
Conversely, mumps, measles, rubella and polio will all kill you or leave you maimed, and COVID can potentially do the same thing. There are some rare cases for of real vaccine side effects, but it's exponentially lower than actual COVID risks, so not really sure what you are on abou