There were at least a couple of thousand cases, IIRC from the class action we were involved in (dropped when Blair ended Legal Aid for these cases). The lawyers said my son's case was unusually strong as we had lots of evidence he was cognitively 'normal' not long before the vaccination. One part of my course was standard assessments for pre-school kids and I was the only grad student with a baby so we'd used him as our guinea pig for a massive battery of tests.
In his case, it was clear that very day something had happened.
But in most cases it was less clear cut, I understand, though no less a fact.
Older child vaccinated same day from same batch - probably off schedule as we'd been abroad - had no ill effects. And this was not uncommon. Whatever happened it seemed to affect the babies vaccinated not the slightly older kids. Various theories re. etiology that at this remove in time, I no longer recall.
The lawyers who told me our case was a strong one, had seen hundreds.
Son is now at uni - but couldn't read til he was 17, and still has difficulties. But he is very bright and on course for a First, apparently. He left school with no GCSEs. My younger kids had vaccinations all but MMR. I'm not anti vaccines, as such, just that one.
IIRC (and I might not) there were 3 drugs companies involved in the manufacture of the vaccine that damaged kids (allegedly). The class action had gone so far as to track all the batch numbers and they were seeing clusters of damaged kids around specific batches, which the parents at the time they joined the class action, would have had no way of knowing. But that was a pattern that was emerging. IIRC my son was one of half a dozen or so babies damaged from that one batch. But some others involved more kids. There was some speculation it might be in the storage protocol. Other theories too.
My son's dr was struck off not that long after this happened. Not to do with this but clearly she wasn't exactly stellar.
Just saying to OP and others to keep an open mind. I was the world's biggest supporter of vaccines and 'herd immunity' - having been a teacher, before this.
I no longer read about it or follow research. My son will never be compensated - or the other kids involved. With no Legal Aid we had to drop the class action.