Immunogenicity and Safety Study of GSK Biologicals' Herpes Zoster Vaccine GSK1437173A When Co-administered With Prevenar13 in Adults Aged 50 Years and Older

Inclusion Criteria: * Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol. * Written informed consent obtained from the subject prior to performance of any study specific procedure. * A male or female, aged ≥50 YOA at the time of the first vaccination with the study vaccine(s). * Female subjects of non-childbearing potential may be enrolled in the study. * 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 during the entire treatment period and for 2 months after completion of the vaccination series. Exclusion Criteria: * Use of any investigational or non-registered product other than the study vaccines during the period starting 30 days before the first dose of study vaccines (Day -30 to Day 1), or planned use during the study period. * Any medical condition that in the judgment of the investigator would make intramuscular (IM) injection unsafe. * Use or anticipated use of immunosuppressants or other immune-modifying drugs during the period starting six months prior to study start and during the whole study period. This includes chronic administration of corticosteroids (\>14 consecutive days of prednisone at a dose of ≥20 mg/day \[or equivalent\]), long-acting immune modifying agents or i…