Maybe your are thinking of the thought that if you had chicken pox, you were less likely to get measles. I don't think that is entirely true either, but it used to be an accepted belief.
Different pathogen entirely. I don't think there is any actual science behind this, though you're right that it was a widespread belief (as was "cats will suck the life out of a baby" and "you can't get pregnant if you're nursing" etc...).
So is the shingles vaccination the same as the chicken pox vaccination? I had chicken pox as a kid, as did a lot of kids, but thankfully have not had shingles. Yet. I hope I never do.
They have some similarity, but they're not the same.
I hope you never do either.
You have my sympathies! Three outbreaks, wow.
Sadly, that's not uncommon for immune compromised people. Chemo is gonna get you no matter what...
Oatmeal baths I have heard of. I don't remember how my mother treated me other than keeping a very close watch on me so she could keep me from scratching. Wow I hated that! I wanted to scratch so bad! But oatmeal wasn't a treatment back then.
Socks on the hands to prevent scratching was also popular. Big thick ones.