Study to Evaluate GSK Biologicals' Herpes Zoster Vaccine GSK1437173A in Adults Aged >= 50 Years

Inclusion Criteria:

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

For this study population, non-childbearing potential is defined as current tubal ligation, hysterectomy, ovariectomy or post-menopause.

OR 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 urine 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 vaccine within 30 days preceding the first dose of study vaccine, or planned use during the study period;
• Concurrently participating 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;
• Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease or immunosuppressive/cytotoxic therapy;
• History of HZ;
• Previous vaccination against varicella or HZ;
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. Additionally, consider allergic reactions to other material or equipment related to study participation;
• Significant underlying illness that in the opinion of the investigator would be expected to prevent completion of the study;
• Receipt of immunoglobulins and/or any blood products within the 90 days preceding the first dose of study vaccine or planned administration during the study period;
• Administration or planned administration of any other immunizations within 30 days before the first or second study vaccination or scheduled within 30 days after study vaccination. However, licensed non-replicating vaccines may be administered up to 8 days prior to each dose and/or at least 14 days after any dose of study vaccine;
• 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 enrollment;
• Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose.
• Pregnant or lactating female;
• Female planning to become pregnant or planning to discontinue contraceptive precautions.