Did Vaccine Cause My Son's Autism?

I am sorry to hear that you are going through some difficult times. There were concerns about vaccine being related to autism. A lot of research has gone into looking in to this and we now are certain it is not related to vaccinations. Most communication and language issues do not come to fore before 6-9 months of age: That is, even if a baby was going to have this kind of problems you would not be able to guess.
The heartening thing is that there are a lot of specialists and therpaists who can assess and help out children in most major cities in India. I am sure you are in good pair of hands. Early intervention is important.
Something as unexpected as autism especially as you say with no family history we often try to find explanations. Vaccine I can reassure you is not directly related to this.
Was there high fever with very prolonged ( Hours and hours ) of crying after vaccines in the first 2-3 months? Although even that is not related to autism directly if such thing occurred make sure you have got him seen by a pediatric neurologist.