There is a simple reason why this is not relevant, take the following facts:* children take vaccines* autism displays its first symptoms in childhood* children under the age of 5 make up ~7% of the population* there are ~306 million people in the U.S.
* about 80% of children are vaccinated entirely
This means 306 x 0.07 x .8 = 1.7 million children (roughly) have been vaccinated. With the vaccination schedule being what it is, then, there are somewhere around 100,000 children getting a shot every month (that last one is hand-wavey, it assumes a lot about frequency distributions, but that's not really germane to my point). Autism rates are estimated at anywhere between 1 in 100 and 1 in 150 children, that means we have about 17,000 diagnosis of autism. If every single one of those autism diagnosis was given to a vaccinated child (they're not, but again for our sake here it introduces very small error), and those 17,000 have a scatter distribution of vaccination patterns, that means not one, not dozens, not hundreds, but *thousands* of those diagnosis came within days or weeks of a vaccination: yes, this means that dozens will occur within an hour of a vaccination.
Put those thousands of people together on a message board (and since autism is hard to deal with, a very high percentage of these family *do* bond together, like SMA sufferers or MS or cancer or any other family-impacting disease), you'll have a few thousand people all saying to each other, "Gee... MY kid got a shot right before her symptoms started showing, too! There are thousands of us! THAT CAN'T BE A COINCIDENCE."
But you can see, it actually *isn't* a coincidence... it's exactly what we would EXPECT to happen.