Only kinda, Children’s Aid Society of Peel(Region) v. H.(T.M.C.) (2008) Showed that a mother being vaccine negligent could have the kids taken away temporarily to receive medical care, but the kids didn’t die.

It showed that not vaccinating your child could be considered negligent

For letting children die of negligence, sure. Whether lack of vaccination can be considered negligence, I dunno. A quick search for Canadian cases didn’t turn up anything.