- Evidence of a personally signed and dated informed consent document.
- Willing and able to comply with study procedures.
- Healthy adults 65 to 85 years of age.
- Male subjects or female subjects who are not of childbearing potential.
- Ability to be contacted by telephone during study participation.
- 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 through conclusion of the study.
- Previous administration of an investigational C difficile vaccine or C difficile
monoclonal antibody therapy.
- Proven or suspected prior episode of C difficile infection.
- Unstable chronic medical condition or disease requiring significant change in therapy
or hospitalization for worsening disease within 8 weeks before receipt of
- Serious chronic medical disorders, including metastatic malignancy, severe chronic
obstructive pulmonary disease (COPD) requiring supplemental oxygen, end-stage renal
disease with or without dialysis, clinically unstable cardiac disease.
- Any bleeding disorder or anticoagulant therapy that would contraindicate intramuscular
- Any contraindication to vaccination or vaccine components, including previous
anaphylactic reaction to any vaccine or vaccine-related components.
- Subjects who may be unable to respond to vaccination due to:
- Congenital or acquired immunodeficiency.
- Receipt of systemic corticosteroids (greater than or equal to 20 mg/day of
prednisone or equivalent) for greater than or equal to 14 days within 28 days of
- Receipt of chronic systemic treatment with other known immunosuppressant
medications, or radiotherapy, within 6 months of enrollment.
- Underlying bone marrow disorder treated within the past year, such as
myelodysplasia, myeloma, or myeloproliferative disorder, treated within the past
year, or any history of bone marrow transplant.
- Malignancy that required treatment with chemotherapy (including the use of
adjunctive and hormonal therapy), immunotherapy, radiation therapy, or
antineoplastic target therapies within the past 24 months.
- Receipt of blood products or immunoglobulins within 6 months before enrollment through
conclusion of the study.
- Residence in a nursing home or other long-term care facility, or 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.
- A known infection with human immunodeficiency virus (HIV).
- Other acute or chronic medical or psychiatric condition including recent (within the
past year) or active suicidal ideation or behavioral 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.
- Female subjects of childbearing potential; pregnant female subjects; breastfeeding
female subjects; fertile male subjects who are unwilling or unable to use a highly
effective method of contraception as outlined in this protocol for the duration of the
study and for at least 28 days after the last dose of investigational product.