Safety and Immunogenicity of Different Dosing Schedules of GlaxoSmithkline (GSK) Biologicals' Herpes Zoster (HZ) Vaccine in Adults 50 Years of Age or Older

The purpose of this study is to assess the safety and immunogenicity of the GSK Biologicals' HZ vaccine 1437173A administered on either a 0,2-; 0,6- or 0,12-month schedule in adults aged 50 years or above, as the immunogenicity of the HZ vaccine administered at intervals longer than two months is not known.

Subjects in each group will be stratified by age with a minimum of 35 subjects in each stratum (50-59 years of age (YOA) stratum, 60-69 YOA stratum and ≥ 70 YOA stratum).

Eligibility Criteria:
Inclusion Criteria:

* Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
* A male or female aged 50 years or older at the time of the first vaccination.
* Written informed consent obtained from the subject.
* Female subjects of non-childbearing potential may be enrolled in the study.

  * Non-childbearing potential is defined as pre-menarche, current tubal ligation, hysterectomy, ovariectomy 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 during the entire treatment period and for two months after completion of the vaccination series.

Exclusion Criteria:

* Use of any investigational or non-registered product other than the study vaccine within 30 days preceding the first dose of study vaccine, or planned use during the study period.
* Chronic administration 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 a live vaccine in the period starting 30 days before and ending 30 days after either dose of study vaccine.
* Administration or planned administration of a non-replicating vaccine within eight days prior to or within 14 days after either dose of study vaccine.
* Administration of long-acting immune-modifying drugs (e.g. infliximab) within six months prior to the first vaccine dose or expected administration at any time during the study period.
* Previous vaccination against varicella or HZ (either registered product or participation in a previous vaccine study).
* Planned administration during the study of an HZ or varicella vaccine (including an investigational or non-registered vaccine) other than the study vaccine.
* History of HZ.
* History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine(s).
* Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease (e.g. malignancy, human immunodeficiency virus \[HIV\] infection) or immunosuppressive/cytotoxic therapy (e.g. medications used during cancer chemotherapy, organ transplantation or to treat autoimmune disorders).
* Acute disease and/or fever at the time of enrolment.

  * 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.
* Administration of immunoglobulins and/or any blood products within the three months preceding the first dose of study vaccine or planned administration during the study period.
* 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.
* Pregnant or lactating female.
* Female planning to become pregnant during the entire treatment period and for two months after completion of the vaccination series, or planning to discontinue contraceptive precautions (if of childbearing potential).