I should preface this that because of strong genetic predisposition for autism in my family, we selectively vax our kids. That said, the only specific vaccine that has significant theory behind it that may tie it to autism is the MMR vaccine. Also, autism is not CAUSED by vaccinations. Some theorize that autism, in children who are already genetically predisposed to it, can TRIGGER it. But, no, vaccines are not the cause of autism. Additionally, since your child is already fully vaccinated, he should be completely fine.
Also, if you look at the risks associated with the actual disease processes for certain vaccines, you will realize that many of the young childhood vaccines prevent diseases that are not significantly more dangerous than the vaccines themselves. For instance, children generally don't contract measles or mumps until after one year, at which time their immune systems are stron enough to withstand most significant long term effects of the virus. Unfortunately, meningitis, if it doesn't cause death (and a quick one at that), often causes very damaging, life altering, long term effects. While the benefit is about the same as the risk in the case of the MMR vaccine, the benefit FAR outweighs the risk for the meningococcal vaccine.
Not only that, but if your child does not have autism by the time he is about 3.5, he won't ever get it. So there is no risk in him developing autism by the time he is 11.