Safety and Immunogenicity Study of GSK's Clostridium Difficile Vaccine 2904545A When Administered in Healthy Adults Aged 18-45 Years and 50-70 Years

Inclusion criteria

• Subjects who, in the opinion of the Investigator, can and will comply with the requirements of the protocol.
• Written or witnessed/thumb print informed consent obtained from the subject prior to performance of any study specific procedure.
• For Step 1 only: A male or female between, and including, 18-45 years of age at the time of the first vaccination.
• For Steps 2, 3, and 4: A male or female between, and including, 50-70 years of age at the time of the first vaccination.
• Healthy subjects as established by medical history and clinical examination before entering into the study.
• Subjects free of any uncontrolled chronic illnesses as established by medical history and clinical examination before entering into the study.
• Female subjects of non-childbearing potential may be enrolled in the study.

• Non-childbearing potential is defined as premenarche, current bilateral tubal ligation or occlusion, hysterectomy, bilateral 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 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

• Health condition that, in the opinion of the Investigator, may interfere with optimal participation in the study or place the volunteer at increased risk of AEs. Study clinicians, in consultation with the Principal Investigator will use clinical judgment on a case by case basis to assess safety risks under this criterion. The Principal Investigator will consult with the Medical Monitor as appropriate.
• Use of any investigational or nonregistered product other than the study vaccine(s) during the period starting 30 days before the first dose of study vaccine(s) (Day 29 to Day 1), or planned use during the study period.
• Any medical condition that in the judgment of the Investigator would make IM injection unsafe and subjects under treatment with anticoagulant therapy.
• Chronic administration of immunosuppressants or other immune modifying drugs during the period starting 3 months prior to the first vaccination. For corticosteroids, this will mean prednisone ≥ 5 milligrams per day (mg/day) (for adult subjects), or equivalent. Inhaled and topical steroids are allowed.
• Administration of long acting immune modifying drugs at any time during the study period.
• Administration of immunosuppressive therapy, including chemotherapeutic agents used to treat cancer or other conditions, and treatments associated with organ or bone marrow transplantation or autoimmune disease.
• Administration of immunoglobulins and/or any blood products during the period starting 3 months before the first vaccination of study treatment or planned administration during the study period.
• Planned administration/administration of a vaccine not foreseen by the study protocol in the period starting 6 weeks before the first vaccination and ending 6 weeks after the last vaccination, with the exception of inactivated influenza vaccine which can be administered up to 14 days before or from 30 days after the last study vaccination.

In case an emergency mass vaccination for an unforeseen public health threat (eg, a pandemic) is recommended and/or organized by public health authorities outside the routine immunization program, the time period described above can be reduced if, necessary for that vaccine, provided it is used according to the local governmental recommendations and that the Sponsor is notified accordingly.

• Planned administration of GSK's Herpes Zoster vaccine marketed as Shingrix or an adjuvanted recombinant varicella zoster virus envelope gE subunit vaccine (HZ/su) within 180 days before the first dose and within 180 days after the last dose of the study vaccine.
• Planned elective surgery 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.
• Body mass index < 19 kg/m^2 or ≥ 35 kg/m^2.
• Clinically relevant physical examination abnormalities.
• For subjects aged 18 - 45 years, Grade 2 or higher abnormal hematological, biochemical, and urinary parameters.
• For subjects aged 50 - 70 years, Grade 3 or higher abnormal hematological, biochemical, and urinary parameters.
• Documentation of current or prior episode of CDI.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).
• Recurrent history or uncontrolled neurological disorders or seizures.
• Family history of congenital or hereditary immunodeficiency.
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccines.
• Acute disease and/or fever at the time of enrollment.

• Fever is defined as temperature ≥ 38.0°C/100.4°F. The preferred location for measuring temperature in this study will be the oral cavity.
• Subjects with a minor illness, without fever, may be enrolled at the discretion of the Investigator.
• Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic, or renal functional abnormality, as determined by physical examination or laboratory screening tests.
• Pregnant or lactating female.
• History of intestinal bleeding or history of diverticular intestinal bleeding.
• Surgery for gastrointestinal malignancy in the period starting 3 months prior to the first vaccination.
• History of chronic alcohol consumption and/or drug abuse as deemed by the Investigator to render the potential subject unable/unlikely to provide accurate safety reports.
• Female planning to become pregnant or planning to discontinue contraceptive precautions.
• Documented human immunodeficiency virus positive subject, known positivity for the surface antigen of the hepatitis B virus or known positive serologic test for the hepatitis C virus.
• Involvement in the planning and/or conduct of the study.