Check how long it is effective. That is one problem with the chicken pox vax. It wears off, and then the immunuzed are at risk again, only older when it is harder to handle. A mild shingles may be preferable. (I stress MAY be. I got lucky with mine.) Anyway, something else to ask. And does it help those who have already had an outbreak? And is it one of those that makes you temporarily contagious to those who did not have chicken pox? (Live virus types. With my shingles, I had to avoid my pregnant friend because you are chicken pox contagious.)