if there are cases children suffered from regress and end up with autism after taking MMR, actually got statistics show that,...
then you would be falling prey to the
post hoc ergo propter hoc logically fallacy.
Just because A follows B (sometimes), it does not mean that A causes B. That is not a valid assumption you can make. More is needed.
In the MMR/autism situation, the fact that autism mostly
doesn't follow MMR vaccination ought to suggest to you that there's likely to be other causes of autism that have nothing to do with MMR. And, in fact, we
expect a correlation between a child with autism having the MMR vaccine and showing symptoms of autism. It's because the MMR vaccine is typically given to children at an age when, if they are autistic, the signs first start to become visible. In other words, A (the MMR vaccine) doesn't cause B (a diagnosis of autism), even though B often follows A in children who have autism (for other, non-MMR-related reasons).
another possible case is may be the batch of vaccine got higher contents of mercury, and cause damage to the brain of the child.
In referring to mercury in vaccines, you can only be relying on the same set of thoroughly debunked sources that made false links between MMR and autism.
Which source are you using to find out about mercury in the MMR vaccine? Is there mercury in? Can you confirm that? Was there
ever mercury in it? Has anything changed in recent years (since the original fraudulent study by Wakefield was published)?
Have you actually researched any of this, yourself? What did you find?
Please list the references you consulted.
In particularly, you refer vaguely to "statistics" that show regression in children after having the MMR vaccine. Please cite your reference for those "statistics". Where can I see them?