How old is your son? Would it mean waiting quite a bit longer to do it at one year?
If he has 3 shots he is not only getting more vaccinations but also more of the carrying agent which is full of nasty substances.
Have you seen this thread?
http://forum.brillkids.com/coffee-corner/autism-and-vaccines/ I realize it is probably about MMR more than other vaccinations, but it has some good info.