More specifically, it's highly doctor-dependent. The FDA hasn't approved shingrix for people under 50; some doctors are willing to prescribe it without FDA approval, others are not. I personally had shingles in my early thirties and have thus far been unable to have my doctor prescribe shingrix.

Also, I would like to point out that having shingles was possibly the single most physically unpleasant experience of my life and boy it sure would have been fantastic to have been able to get the shingles vaccine before I got shingles, as opposed to sometime after! because wow, having shingles sucks.