It has since emerged that dozens of other families have reached similar settlements, and the Centers for Disease Control in the US has announced new research into vaccine safety.

Consider this, too: while we still don't know exactly what causes autism, the latest research – including the study released by Dr Amaral of the University of California last week – is coalescing around the view that it's a combination of genetic, immune system and environmental factors. Earlier this year, Dr Amaral said that, "there is a small subset of children who may be particularly vulnerable to vaccines if the child had a precondition like a mitochondrial defect ... vaccinations, for those children, may be the environmental factor that tipped them over the edge."

So why hasn't this come up in vaccination studies to date? Dr Martha Herbert, professor of neurology at Harvard Medical School, says, "the problem with the population studies is they aren't necessarily designed to have the statistical power to find subgroups like that if the subgroups are small."

That means we're not studying the right kids. We don't even know where to find them, because most of the time we don't know they have those vulnerabilities until they're aggravated. Herein lies the great mystery.

So where do I stand on this? I'm not a parent. I haven't yet had to make the agonising decision about whether or not to vaccinate my child. But I do know this: I'm definitely pro-vaccines and understand all too well the benefits they bring, and I also know they're toxic for some kids. Because I saw what happened in the case of one of my nephews, for whom vaccination was one of several environmental factors and assaults to his immune system that, along with genetic predisposition and an underlying vulnerability, stressed his body and his mind so much that he slipped into autism. It's not a conclusion that his mother, a sober individual pushing 40 with an honours degree in science and a background in public health, wanted to reach, but in the end it was undeniable.