How Long Does Shingles Vaccine Take To Show Effect?

I read where if I get a vaccine for shingles to stay away from people that haven't yet had a chickenpox vaccine like my grandchildren. How long am I supposed to stay away from them should I wait on my vaccine I have 4 grandchildren under 3 they do keep up on their shots but don't know if some are old enough for their shots Also I have a family member whos immune system is low from a medicine he takes for As will this affect him?