Safety and Immunogenicity Study of GSK Biologicals' Herpes Zoster Subunit (HZ/su) Vaccine GSK1437173A When Administered Subcutaneously Intramuscularly in Adults Aged ≥50 Years

Inclusion Criteria: * Subject who, in the opinion of the investigator, can and will comply with the requirements of the protocol. * Subject, residing in Japan, is of Japanese ethnic origin, defined as having been born in Japan with four ethnic Japanese grandparents and able to speak Japanese. * Subject has provided written informed consent. * Subject, male or female, who is 50 YOA or older at the time of the first vaccination. * Subject, if female, of non-childbearing potential may be enrolled in the study. * Subject, if female, 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 (i.e., for 2 months after Month 2). * Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine within 30 days preceding the first dose of study vaccine, or planned use during the study period. * Concurrently participating or planned participation in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational product. * Administration or planned administration of a live vaccine within 30 days prior to the first study vaccination through 30 days after the second study vaccination. * Administration or planned administration of a non-replicating vaccine within 8 days prior to or within 14 days after either dose of study vaccine. * Planned administration, during the study, of an HZ or varicella vaccine (including an investigational or non-registered vaccine) other than the study vaccine. * Administration of immunoglobulins and/or any blood products within the three (3) months preceding the first dose of study vaccine or planned administration during the study period. * Chronic administration (defined as \>14 consecutive days) of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose. * For corticosteroids, a prednisone dose of \<20 mg/day, or equivalent, is allowed. * Inhaled, topical, and intra-articular corticosteroids are allowed. * Administration or planned administration of long-acting immune-modifying drugs (e.g., infliximab) within six months prior to the first vaccine dose through the duration of the study period. * History of HZ. * Previous vaccination against HZ or varicella (registered or investigational product). * History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine or study material and equipment. * Significant underlying illness that, in the opinion of the investigator, would be expected to prevent completion of the study. * Any other condition that, in the opinion of the investigator, might interfere with the evaluations required by the study. * Acute disease and/or fever at the time of vaccination: * Fever is defined as temperature ≥37.5°C (99.5°F) for oral, axillary, or tympanic route, or ≥38.0°C/100.4°F for rectal route. The preferred route for recording temperature in this study will be oral. * Subjects with a minor illness (such as mild diarrhoea, mild upper respiratory infection) without fever may, be enrolled at the discretion of the investigator. * Pregnant or lactating female. * Female planning to become pregnant or planning to discontinue contraceptive precautions (if of childbearing potential) through Month 4 (i.e., 2 months after the second dose of study vaccine).