Yeah, that stuff is damn nasty.
Had to train cannibals to not eat the brains, over that stuff.
I wouldn't doubt that some of the lots of VAXXX had them in it.
But, when it is only 1 out of a 100, and each is slightly different. It becomes impossible to pin anything down, and find the cause. Or to take BigPharma to court over turning someone's brain to mush.