I wonder how these parents are going to react when their kids die from this or, at the very least and if they are lucky, the children will never reproduce because they are sterile.

They'll find a way to dodge the blame. Very likely say that the vax deaths were due to a variant created by the unvaxxed. Everything would have been fine if everyone trusted the science (ignoring the fact that there are multiple animal host for c-19, both wild and domesticated, meaning that it's going to continue to mutate and come back literally forever even if everyone on the planet got a 100% effective vaccine tomorrow).