1. Evidence of a personally signed and dated informed consent document.
2. Healthy male and female adults aged 50 to 85 years at enrollment as determined by
medical history, physical examination, and the clinical judgment of the investigator
to be eligible for the study. Subjects with preexisting chronic medical conditions
determined to be stable may be included.
3. Male subjects who, in the opinion of the investigator, are biologically capable of
fathering children, and who are sexually active with women of childbearing potential
must agree to use a highly effective method of contraception from the time of informed
consent through at least 28 days after the last dose of investigational product
(through Visit 9 at Month 7).
4. Female subjects who are not of childbearing potential (ie, meet at least one of the
- Have undergone hysterectomy or bilateral oophorectomy;
- Have medically confirmed ovarian failure or
- Are medically confirmed to be postmenopausal
5. Availability for the entire duration of the study, and able to comply with scheduled
visits, treatment plan, laboratory tests, and other study procedures including
completion of the electronic diary (eDiary) from Day 1 to Day 7 following each
6. Ability to be contacted by telephone during study participation.
1. Previous administration of an investigational C. difficile vaccine or C. difficile
monoclonal antibody therapy.
2. Proven or suspected prior episode of CDAD.
3. Unstable chronic medical condition or disease requiring significant change in therapy
or hospitalization for worsening disease within 12 weeks before receipt of study
4. Serious chronic medical disorders including metastatic malignancy, severe chronic
obstructive pulmonary disease (COPD) , end stage renal disease with or without
dialysis, clinically unstable cardiac disease, or any other disorder that in the
investigator's opinion precludes the subject from participating in the study.
5. Donation of blood volume of 250 mL or greater, or donation of plasma within 3 months
prior to enrollment or during the conduct of the study.
6. Bleeding diathesis or condition associated with prolonged bleeding time that may
contraindicate intramuscular injection or blood draw including subjects taking
anticoagulant, antiplatelet and/or antithrombotic agents except for low dose daily
aspirin (?325mg per day) within 30 days before enrollment through completion of Visit
9 (Month 7).
7. Any contraindication to vaccination or vaccine components.
8. "Immunocompromised persons or subjects currently on immunosuppressive therapy or with
a history of immunosuppressive therapy, including chemotherapy agents for treatment of
diseases including, but not limited to cancer, inflammatory bowel disease or
autoimmune disease. Recent history (within the past 6 months) of long term (7 days or
longer) systemic corticosteroid use."
9. Subjects who received oral or parenteral antibiotics within 1 month before enrollment.
Topical antibiotics are allowed.
10. Receipt of blood products or immunoglobulins (including monoclonal antibodies) within
6 months before enrollment through conclusion of the study.
11. Participation in other investigational or interventional studies within 30 days before
the current study begins and/or during study participation. Participation in purely
observational studies is acceptable.
12. Subjects who are investigational site staff members or relatives of those site staff
members, or subjects who are Pfizer employees directly involved in the conduct of the
13. Females of childbearing potential; males of childbearing potential not using highly
effective contraception or not agreeing to continue highly effective contraception for
at least 28 days after last dose of investigational product (through Visit 9 at Month
14. Females receiving exogenous estrogen therapy.
15. Residence in a nursing home, long-term care facility, requirement for semiskilled
nursing care or assisted living. An ambulatory subject who lives in an autonomous
manner in a retirement home or village is eligible for the trial.
16. Any abnormality in screening hematology and/or blood chemistry laboratory values
according to the toxicity grading scale. Subjects with stable Grade 1 abnormalities
for hemoglobin, leukocyte count, and platelets may be considered eligible at the
discretion of the investigator.
17. A positive screening test or known infection with human immunodeficiency virus (HIV),
hepatitis B virus (HBV) and/or hepatitis C virus (HCV).
18. Other severe acute or chronic medical or psychiatric condition or laboratory
abnormality that may increase the risk associated with study participation or
investigational product administration or may interfere with the interpretation of
study results and, in the judgment of the investigator, would make the subject
inappropriate for entry into this study.