This is not politically correct and I apologize, but my dad said growing up in the 60s and 70s that there was “always that one weird kid” in the back of all his classrooms who never made friends and had trouble sitting still or doing the schoolwork. He said he realizes now that they were all possibly autistic. Autistic kids have always been around, but we can better diagnose and help them now. 

Also of note, my dad is deaf in one ear, probably caused by measles when he got it when he was 3 or 4. The vaccine was just getting popular when he was young and he never got it. Sure, it didn’t kill him but it left him with a life long disability (although luckily it doesn’t affect him that much and he’s adjusted to it). 