Good luck! If you have a way to prevent shingles "Naturally", maybe it should be written up and submitted to a medical journal. A Nobel Prize in Medicine might be in the offing for you!
Oh - I know, "Strengthen your immune system". I'm not so sure I'd want to mess with my immune system even if it could be scientifically proven (it can't) that "Natural" measures really can do something. An over-activated immune system can lead to quite a number troublesome auto-immune diseases: