It can range from a mildly irritating skin rash to something almost debilitatingly painful. Length of time it lasts various a great deal also. That said I have no idea of the efficacy of the vaccine
I had an extremely mild case about 30 years ago caught early and treated with antivirals. But I have known some people who have suffered. I guess like everything in life it’s a crapshoot
My wife had it for a month which was painful but she tolerated it pretty well. It was on one side of her back.