A Study To Investigate Two 3-dose Schedules Of A Clostridium Difficile Vaccine In Healthy Adults Aged 65 to 85 Years

A PHASE 2, PLACEBO-CONTROLLED, RANDOMIZED, OBSERVER-BLINDED STUDY TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF TWO 3-DOSE REGIMENS OF A CLOSTRIDIUM DIFFICILE VACCINE IN HEALTHY ADULTS AGED 65 TO 85 YEARS

This study will investigate a Clostridium difficile vaccine in healthy adults aged 65-85 years. Each subject will initially receive 3 doses of vaccine on 1 of 2 vaccination schedules. The study will assess the safety and tolerability of the vaccine as well as the subjects' immune response to the vaccine. One year after the third dose subjects that did not receive placebo will be randomized to receive a fourth dose. Subjects will be followed for up to 4 years after their third vaccination.

Inclusion Criteria:

• Healthy male and female subjects
• Aged 65 to 85 years

Additional Inclusion Criteria for the extension Stage:

• Receipt of all 3 doses of C difficile vaccine (100 µg or 200 µg antigen dose level) in the original portion of the study.

Exclusion Criteria:

• Proven or suspected prior episode of Clostridium difficile associated diarrhea
• Unstable chronic medical condition
• Disease requiring significant change in therapy or hospitalization for worsening disease within 8 weeks before receipt of study vaccine
• Serious chronic disorders
• Congenital or acquired immunodeficiency disorders
• Rheumatologic disorders or other illnesses requiring chronic treatment with known immunosuppressant medications.
• Active or treated leukemia or lymphoma or bone marrow disorder
• Any contraindication to vaccination or vaccine components including previous anaphylactic reaction to any vaccine or vaccine-related components

Additional Exclusion Criteria for the Extension Stage:

• Subjects originally randomized to placebo during the original portion of the study.
• Subjects who have already completed Visit 9 prior to study unblinding.