I got the vaccines and booster shots when i was a kid and still got chickenpocks. And all the other ones too!
My kids got it twice!
Once when they were under a year old, not too serious a case.
Then again when they were about three. Apparently the immune system isn’t fully mature when they are babies.
One of my kids came up to me, point to his arm, and said, “I have a ‘chicken pock’.” It turned out he was correct!