You could claim the timing is a confounding variable since vaccine are so rigorously scheduled. Perhaps a developmental period where autism symptoms begin to show overlaps with the time that, say, the MMR vaccine is scheduled (first shot typically given when 12-15 months old). You could compare vaccine/autism symptoms timing just for children who were vaccinated on an alternative schedule. The only problem you might run into is if later vaccination actually reduces the risk for vaccine-induced autism for certain shots. Shouldn't we be asking these people to prove the *benefit* of these vaccines though? Does the MMR shot at 12-15 months age actually reduce outbreaks of measles and is it necessary/desirable to reduce these outbreaks? Why aren't they being asked to prove that? If they claim to know this, I want to see the receipts.