The first-in-Japanese study B5091010 has been designed to evaluate the safety, tolerability, and immunogenicity of 2 antigen dose levels of C difficile vaccine when administered as one of two 3-dose regimens to healthy Japanese adults aged 65 to 85 years.

Inclusion Criteria:

1. Healthy male and female adults
2. Aged 65 to 85 years

Exclusion Criteria:

1. Proven or suspected prior episode of Clostridium difficile associated diarrhea
2. Unstable chronic medical condition
3. Disease requiring significant change in therapy or hospitalization for worsening disease within 8 weeks before receipt of study vaccine
4. Serious chronic medical disorders
5. Bleeding diathesis or condition associated with prolonged bleeding time that may contraindicate intramuscular injection
6. Any contraindication to vaccination or vaccine components, including previous anaphylactic reaction to any vaccine or vaccine-related components
7. Subjects with congenital or acquired immunodeficiency disorders
8. Subjects with rheumatologic disorders or other illnesses requiring chronic treatment with known immunosuppressant medications
9. Active or treated leukemia or lymphoma or bone marrow disorder
10. Residence in a nursing home or other long-term care facility, or requirement for semiskilled nursing care or assisted living
11. Abnormality in screening hematology and/or blood chemistry laboratory values