My daughter had the vaccine as a baby. Then for a surprise 7th birthday present last year, she got the chicken pox! It was mild though. No vaccine is 100% effective, and that one has a lower success rate than some.
Shingles isn’t what happens when an adult is exposed to chicken pox. That would be a super-hellacious bout of flulike pox. The herpesvirus that causes chicken pox remains latent in the system of the people who have had it, to reactivate in later life along the nerves. That’s shingles- so it affects people who’ve already had chicken pox, not the never exposed.