What are the reasons that people believe autism is related to immunizations?

Age of vaccination: Autism is generally diagnosed in children under the age of 5 years. This is also when most children receive the bulk of their childhood vaccinations. This does not mean that one causes the other. Most toddlers fall down and bump their heads, but this isn't blamed on vaccinations. Their are many causes of autism, but most experts agree that they are not the cause of autism.

Looking for answers: We want answers. What is it, why did it happen (so we can avoid it in the future) and can it be fixed?Conditions with poor explanation like autism or crib death give rise to speculation & both have been tagged as vaccine related on occasion.As research provides better answers the idea fades.New microarray technology has shown small chromasomal defects in many autism pts.This research is promising.

Bad science: Bad science and misinformation. There is a small minority of people who are always suspicious of vaccination. Their concerns were fueled and spread when a scientist published an article linking autism to vaccination. He later had to retract his article for faulty science, but the damage was already done.