Evaluation Of Clostridium Difficile Vaccine Lot Consistency In Healthy Adults 65 To 85 Years Of Age

This study will investigate a Clostridium difficile vaccine in healthy adults 65 to 85 years of age, who will each receive 3 doses of vaccine. The study will assess the lot consistency, safety, and tolerability of the vaccine, and also look at the subjects' immune response to the vaccine.

Serology for B5091008 was delayed due to discussions with the FDA on statistical analysis as well as delays attributed to the COVID pandemic.

Eligibility Criteria:
Inclusion Criteria:

* 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.

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 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 investigational product.
* 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 injection.
* 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 enrollment.
  * 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.