I think collecting whortleberries was quite a big thing in my part of rural Surrey too, right up till the time my father was a boy. The usual Surrey name for them was "hurts", presumably just an abbreviation of whortleberry. There's an area known as Hurtwood not far from where I live.

Aw, that's cool!

And, yes, although it wasn't so much the vaccines as the invention of drugs that could actually handle them (vaccines as well), but those came in during the 1940s and were the biggest game changer in that respect, because you could treat a fever, rather than just nursing and waiting for the crisis. (Sulphanilomides?? first and then Penicillin, of course.)