To Understand the Safety and Effects of a C. Difficile Vaccine With New Adds-Ons That Will Be Given to Healthy Adults

Inclusion criteria

• Each phase of the study will enroll participants in different age categories:

Phase 1: Participants ≥65 to <85 years of age; Phase 2: Participants ≥65 years of age; Cohort 4 Participants 50 through 64 years of age.

• Healthy participants as determined by medical history, clinical assessment, and the judgment of the investigator.
• Participants who are willing and able to comply with all scheduled visits, investigational plan, laboratory tests, lifestyle considerations, and other study procedures.
• Capable of giving personally signed informed consent, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol.

Exclusion criteria

• Fertile male participants and WOCBP who are unwilling or unable to use an effective method of contraception from the signing of informed consent until at least 28 days after the last dose of study intervention.
• Serious chronic disorder, including history of metastatic malignancy, severe COPD requiring supplemental oxygen, end-stage renal disease with or without dialysis, cirrhosis of the liver, clinically unstable cardiac disease, or any other disorder that, in the investigator's opinion, would make the participant inappropriate for entry into the study.
• Any contraindication to vaccination or vaccine components, including previous hypersensitivity or anaphylactic reaction to any vaccine or vaccine-related components.
• Prior episode of CDI, confirmed by either laboratory test or diagnosis of pseudomembranous colitis at colonoscopy, at surgery, or histopathologically.
• Any bleeding disorder or anticoagulant therapy that would contraindicate intramuscular injection.
• Known or suspected immunodeficiency or other conditions associated with immunosuppression, including, but not limited to, leukocyte, lymphocyte, or immunoglobulin class/subclass deficiencies or abnormalities, generalized malignancy, HIV infection, leukemia, lymphoma, or organ or bone marrow transplant.
• Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
• Previous receipt of an investigational C difficile vaccine or C difficile mAb therapy.
• Receipt of blood product or immunoglobulin within 6 months before enrollment.
• Currently receives treatment with immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, or planned receipt throughout the study. Participants may not be enrolled if corticosteroids were administered within 28 days before study intervention administration.
• Participation in other studies involving investigational drugs, investigational vaccines, or investigational devices within 28 days prior to study entry through 12 months after the last dose of study intervention.
• Phase 1 only: Any screening hematology and/or blood chemistry laboratory value that meets the definition of a ≥ Grade 1 abnormality.
• Investigator site staff directly involved in the conduct of the study and their family members, site staff otherwise supervised by the investigator, and sponsor and sponsor delegate employees directly involved in the conduct of the study and their family members.