Bunbaker is absolutely correct in that the medical authorities like WHO made a decision about MMR based on what is best for the vast majority. MMR undoubtedly saves many lives. However, the possibility that be MMR MAY be a trigger for a very small subset of children [there could be a huge number of triggers, more research obviously needed] has been stifled in terms of research, because Wakefield messed it up, the media did massive scaremongering and the public were very scared, so the medical authorities put an end to any possibility of research - for the public good, they felt, because obviously, if loads of kids are not vaccinated against measles, there would be a huge increase in severe illness and deaths from measles [ and complications from the other two illnesses too].
Statistical research would not be very helpful in flagging up this very small possible subset. What it does show though is that MMR is safe for the vast majority.
123 you don't seem to know much about the vaccinations issue though, but if you have any concerns there are single vaccines available, that way you can get your child protected from what are not trivial illnesses, and circumvent the MMR worry, even though as I said, statistical research shows that it is safe for the majority, and the question of whether it can act as a trigger for a small subset of children is still very open-ended [as no research is being done on that matter] Obviously if we all stopped vaccinating there would be more deaths and severe illness from theses diseases.
However, regression is a recognised phenomena, in terms of a child developing normally and then regressing severely. It doesn't happen with all autism cases, but with a significant proportions. here No one knows why this happens and there may be a number of reasons, genetic predisposition, environmental triggers, more research is needed. What is not true however, is that parents just didn't notice before that their children lost all verbal, social and developmental skills. That is deeply unfair to those parents and just against the proven research.