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

Inclusion Criteria:

1. 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 ofage.

2. Healthy participants as determined by medical history, clinical assessment, and thejudgment of the investigator.

3. Participants who are willing and able to comply with all scheduled visits,investigational plan, laboratory tests, lifestyle considerations, and other studyprocedures.

4. Capable of giving personally signed informed consent, which includes compliance withthe requirements and restrictions listed in the ICD and in this protocol.

Exclusion Criteria:

1. Fertile male participants and WOCBP who are unwilling or unable to use an effectivemethod of contraception from the signing of informed consent until at least 28 daysafter the last dose of study intervention.

2. Serious chronic disorder, including history of metastatic malignancy, severe COPDrequiring supplemental oxygen, end-stage renal disease with or without dialysis,cirrhosis of the liver, clinically unstable cardiac disease, or any other disorderthat, in the investigator's opinion, would make the participant inappropriate forentry into the study.

3. Any contraindication to vaccination or vaccine components, including previoushypersensitivity or anaphylactic reaction to any vaccine or vaccine-relatedcomponents.

4. Prior episode of CDI, confirmed by either laboratory test or diagnosis ofpseudomembranous colitis at colonoscopy, at surgery, or histopathologically.

5. Any bleeding disorder or anticoagulant therapy that would contraindicateintramuscular injection.

6. Known or suspected immunodeficiency or other conditions associated withimmunosuppression, including, but not limited to, leukocyte, lymphocyte, orimmunoglobulin class/subclass deficiencies or abnormalities, generalized malignancy,HIV infection, leukemia, lymphoma, or organ or bone marrow transplant.

7. Other medical or psychiatric condition including recent (within the past year) oractive suicidal ideation/behavior or laboratory abnormality that may increase therisk of study participation or, in the investigator's judgment, make the participantinappropriate for the study.

8. Previous receipt of an investigational C difficile vaccine or C difficile mAbtherapy.

9. Receipt of blood product or immunoglobulin within 6 months before enrollment.

10. Currently receives treatment with immunosuppressive therapy, including cytotoxicagents or systemic corticosteroids, or planned receipt throughout the study.Participants may not be enrolled if corticosteroids were administered within 28 daysbefore study intervention administration.

11. Participation in other studies involving investigational drugs, investigationalvaccines, or investigational devices within 28 days prior to study entry through 12months after the last dose of study intervention.

12. Phase 1 only: Any screening hematology and/or blood chemistry laboratory value thatmeets the definition of a ≥ Grade 1 abnormality.

13. Investigator site staff directly involved in the conduct of the study and theirfamily members, site staff otherwise supervised by the investigator, and sponsor andsponsor delegate employees directly involved in the conduct of the study and theirfamily members.