Clostridium Difficile Vaccine Efficacy Trial

Inclusion Criteria:

- Evidence of a personally signed and dated informed consent document.

- Willing and able to comply with study procedures.

- Subjects with an increased risk of future contact with healthcare systems or subjects
who have received systemic antibiotics in the previous 12 weeks.

- Ability to be contacted by telephone during study participation.

- Negative urine pregnancy test for female subjects of childbearing potential.

Exclusion Criteria:

- Investigator site staff members directly involved in the conduct of the study and
their family members, site staff members otherwise supervised by the investigator, or
subjects who are Pfizer employees, including their family members, directly involved
in the conduct of the study.

- Participation in other studies involving investigational drug(s)/vaccine(s) within 28
days prior to study entry until 1 month after the third vaccination.

- Previous administration of an investigational C difficile vaccine or C difficile mAb
therapy.

- Prior episode of CDI..

- Receipt of blood products or immunoglobulins within 6 months before enrollment.

- Subjects who may be unable to respond to vaccination due to:

- Metastatic malignancy; or

- End-stage renal disease; or

- Any serious medical disorder likely to be fatal within the next 12 months; or

- Congenital or acquired immunodeficiency; or

- Receipt of high dose systemic corticosteroids for 14 days within 28 days of
enrollment; or

- Receipt of chronic systemic treatment with other known immunosuppressant
medications, or radiotherapy, within 6 months of enrollment.

- Known infection with human immunodeficiency virus (HIV).

- Any bleeding disorder or anticoagulant therapy that would contraindicate intramuscular
injection.

- Any contraindication to vaccination or vaccine components, including previous
anaphylactic reaction to any vaccine or vaccine-related components.

- Prior small- or large-bowel resection.

- Any condition or treatment resulting in frequent diarrhea.

- Other acute or chronic condition or abnormality that may increase the risk associated
with study participation or IP administration or may interfere with interpretation of
study results

- Pregnant or breastfeeding female subjects; male subjects and female subjects who are
sexually active and at risk for pregnancy and will not/cannot use 2 methods of
contraception