Safety and Immunogenicity Study of GlaxoSmithKline's Herpes Zoster Subunit Vaccine (HZ/su) When Given on a Two-dose Schedule to Adults at Least 50 Years of Age (YOA) With a Prior Episode of Herpes Zoster

Inclusion Criteria: * Subjects and/or subject's LAR(s) who, in the opinion of the investigator, can and will comply with the requirements of the protocol * Written informed consent obtained from the subject/subject's LAR(s) prior to performance of any study specific procedure. * A male or female ≥ 50 YOA at the time of the first vaccination. * Subjects with a history of HZ. Confirmation of the prior HZ diagnosis can be done by one of the following three methods: * Clinically diagnosed HZ: OR Laboratory diagnosed HZ: OR * HZ diagnosed by an adjudication committee: Female subjects of non-childbearing potential may be enrolled in the study. * Non-childbearing potential is defined as current bilateral tubal ligation or occlusion, hysterectomy, bilateral ovariectomy, bilateral salpingectomy or post-menopause. • Female subjects of childbearing potential may be enrolled in the study if the subject: * has practiced adequate contraception for 30 days prior to vaccination, and * has a negative pregnancy test on the day of vaccination, and * has agreed to continue adequate contraception for 2 months after completion of the vaccination series. Exclusion Criteria: * Subjects who at time of study entry or during the maximum period of anticipated study participation are/will become part of the population recommended to receive a zoster vaccine per existing local or national immunization practices will be excluded from study participation. * Use of any investigational or non-regis…