Study to Evaluate the Immunogenicity and Safety of GlaxoSmithKline (GSK) Biologicals' Herpes Zoster Vaccine GSK1437173A When Co-administered With GSK Biologicals' Seasonal Influenza Vaccine GSK2321138A 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 (e.g. completion of the diary cards, return for follow-up visits).
• A male or female aged 50 years or older, at the time of the first vaccination with the study vaccine(s).
• 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 2 months after completion of the vaccination series.

Exclusion Criteria

• Use of any investigational or non-registered product (drug or vaccine) other than the study vaccines within 30 days preceding the first dose of study vaccine, or planned use during the study period.
• Chronic administration (defined as more than 14 consecutive days) of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose (for corticosteroids, this will mean prednisone ≥ 20 mg/day, or equivalent). A prednisone dose of < 20 mg/day is allowed. Inhaled, topical and intra-articular corticosteroids are allowed.
• Administration or planned administration of a vaccine not foreseen by the study protocol within the period starting 30 days before the first dose of study vaccine(s) (HZ/su and/or FLU-D-QIV vaccines) and ending 30 days after the last dose of HZ/su vaccine.
• Administration of an influenza vaccine during the six months preceding entry into the study or planned administration up to the last blood sampling with the exception of the FLU-D-QIV vaccine given during this study.
• 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.
• 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 vaccine/product (pharmaceutical product or device).
• Previous vaccination against VZV or HZ and/or planned administration during the study of a VZV or HZ vaccine (including an investigational or non-registered vaccine) other than the study vaccine.
• History of HZ.
• Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease (e.g., malignancy, HIV infection) or immunosuppressive/cytotoxic therapy (e.g., medications used during cancer chemotherapy, organ transplantation or to treat autoimmune disorders).
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccines.
• History of Guillain Barré syndrome.
• Hypersensitivity to latex.
• 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 on 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 3 months preceding the first dose of study vaccine or planned administration during the study period.
• Pregnant or lactating female.
• Female planning to become pregnant or planning to discontinue contraceptive precautions before 2 months after the last dose of study vaccine.
• Any condition which, in the opinion of the investigator, prevents the subject from participating in the study.
• Any condition which,