If someone already had shingles is it safe to get the zoster vaccine and can it prevent another outbreak?

Can be given age 50. The fda recommends it be offered at age 50 & up. The cdc has not weighed in on the lower age group & still stayed at the 60 year old recommendation for now, partly out of concern for supply. At age 50, there is a better immune response meaning more people can mount a good reaction to the vaccine (69% vs 50%) & become immune to shingles. The shot is very expensive but I do offer it to 50 year old's.
Risk versus benefit. Centers for disease control and prevention recommend a single dose of zoster vaccine for adults aged >60 years, regardless of whether they report a prior episode of herpes zoster . Patients with intact immune systems seldom have recurrences, there is no more risk to a healthy patient who has had zoster, than one who has not as far as is known. Patients with prior zoster have not been studied.
Zostavax can prevent. If someone's already had the shingles, I worry about the state of their immune system. Perhaps they are older and their body is wearing out through aging? Only problem is, the older you get, the less effective the vaccine becomes -- that's just the way it is with aging. I.e. think of that 102 year old - how frail they already are! Definitely would want to protect as this vaccine is safe.