I think this is a reasonable approach to solving the riddle.
Something about vaccines is causing autism and other problems - so many parents see the kids change soon after getting a vaccine. Mercury was the obvious place to start looking for a culprit, but if it isn't mercury that doesn't mean the vaccines are not the problem.
I think they will find it has something to do with the gut flora, and that vaccines changes something there.
Its just an idea, but maybe it is when VACCINES are given soon after or before Antibiotics are given to the kid that the problems start [ Antibiotics kills off good gut flora, and THAT is when vaccines do their damage].