Sorry but i dont think it can be one thing or another and I hate it when people trot out the "it's just more awareness and an increased rate of diagnosis" line as if to say "nothing to see here". There is no proof that this is the only reason for the increase. Lots of things may be contributing that we don't know about.
There clearly are some factors outside of increased diagnosis rates causing an increase. And trust me as a parent of a child with severe autism/LD and probably ASD myself I really don't think the world is suddenly willing to accept and diagnose this more now than before. Have you seen the struggles parents have getting support and education? There are far more cases now than any local authority and health professionals are willing to acknowledge and support. They just can't deny it because the numbers are so high now and it affects lots of NT children, but higher they are higher now than anyone can cope with.
I don't think it is vaccines, but I don't think it is just more people getting diagnosed either. Both are overly simplistic explanations for a complicated genetic disorder that is probably consists of many different disorders rolled are into an umbrella diagnosis.