I don't know the truth.
-from what I've read, mercury is a pwerful neurotoxin, and the suspected reason behind most autism.
Of course, there are other sources of mercury poisoning besides vaccines.
check out this article:
The Age of Autism: Mercury and the Amish
http://washingtontimes.com/upi-breaking/20050518-065621-1970r.htm
I bang my head now ... everytime I hear Helen Thomas.