The problem is that autistic behaviour manifests at about the age children get their MMR and other vaccinations.
I know a truly autistic child. He had a fit after he was given his MMR, and wasn't the same afterwards. It's purely anecdotal, but people infer links between things when they're co-incidental.
I wouldn't do the lolly thing, but I would happily send my kids to a chickenpox party. Get it out of the way.
I had mumps and measles (separately) when I was a kid and didn't suffer any effects, and neither did anyone else in my class. I personally reckon the risks of measles are massively over-inflated in the media
Measles can be nasty, and if you let it loose it will kill, especially people with crap immune systems, it can also
damage your eyesight and the fatality rate in third world countries is 28%, we can deal with it, but it is a serious infection and vaccination is a no brainer.