- Healthy male and female adults aged 50 to 85 years at enrollment
- Proven or suspected prior episode of Clostridium difficile associated diarrhea.
- Unstable chronic medical condition or disease requiring significant change in therapy
or hospitalization for worsening disease within 8 weeks before receipt of study
- Any contraindication to vaccination or vaccine components, including previous
anaphylactic reaction to any vaccine or vaccine-related components