New c. diff vaccine shows promise in preventing dangerous diarrhea
NCT ID NCT05805826
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This study tests new versions of a vaccine to prevent severe diarrhea caused by the C. diff germ. Healthy adults aged 50 and older who have never had a C. diff infection will receive either a new vaccine formula, a previously studied formula, or a placebo. The goal is to see which formula produces the strongest immune response with the fewest side effects.
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Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 1/2
Runs two stages together: safety and dose first, then whether the treatment works.
- Participants
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936 people
The number who actually took part.
- Started
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Mar 2023
- Expected to finish
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Jun 2031
An estimate. End dates often move.
- Lead sponsor
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A company
The lead sponsor is a pharmaceutical, biotech, or medical-device company.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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50 years and older
- Sex
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Anyone
- Healthy volunteers
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Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
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 of age; Cohort 4 Participants 50 through 64 years of age. 2. Healthy participants as determined by medical history, clinical assessment, and the judgment of the investigator. 3. Participants who are willing and able to comply with all scheduled visits, investigational plan, laboratory tests, lifestyle considerations, and other study procedures. 4. 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: 1. 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. 2. 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. 3. Any contraindication to vaccination or vaccine components, including previous hypersensitivity or anaphylactic reaction to any vaccine or vaccine-related components. 4. Prior episode of CDI, confirmed by either laboratory test or diagnosis of pseudomembranous colitis at colonoscopy, at surgery, or histopathologically. 5. Any bleeding disorder or anticoagulant therapy that would contraindicate intramuscular injection. 6. 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. 7. 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. 8. Previous receipt of an investigational C difficile vaccine or C difficile mAb therapy. 9. Receipt of blood product or immunoglobulin within 6 months before enrollment. 10. 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. 11. 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. 12. Phase 1 only: Any screening hematology and/or blood chemistry laboratory value that meets the definition of a ≥ Grade 1 abnormality. 13. 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.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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Alliance for Multispecialty Research, LLC
Doral, Florida, 33172, United States
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Alliance for Multispecialty Research, LLC
Wichita, Kansas, 67226, United States
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Anaheim Clinical Trials, LLC
Anaheim, California, 92801, United States
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BRCR Medical Center Inc.
Plantation, Florida, 33322, United States
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Benchmark Research
Austin, Texas, 78705, United States
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CTI Clinical Research Center
Cincinnati, Ohio, 45212, United States
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Charisma Medical and Research Center
Miami Lakes, Florida, 33014, United States
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Clinical Research Trials of Florida
Tampa, Florida, 33607, United States
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DBC Research USA
Pembroke Pines, Florida, 33029, United States
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Dynamed Clinical Research, LP d/b/a DM Clinical Research
Tomball, Texas, 77375, United States
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Great Lakes Clinical Trials - Ravenswood
Chicago, Illinois, 60640, United States
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HOPE Research Institute
Phoenix, Arizona, 85032, United States
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Indago Research & Health Center, Inc
Hialeah, Florida, 33012, United States
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Miami Clinical Research
Miami, Florida, 33155, United States
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NYU Langone Health
New York, New York, 10016, United States
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New Horizon Research Center
Miami, Florida, 33165, United States
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Prism Research LLC dba Nucleus Network
Saint Paul, Minnesota, 55114, United States
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Private Practice - Dr. Hector Fabregas
Pembroke Pines, Florida, 33026, United States
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Qcare Site Services Inc. d/b/a Avacare
Durham, North Carolina, 27703, United States
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Research Centers of America
Hollywood, Florida, 33024, United States
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Rochester Clinical Research, Inc.
Rochester, New York, 14609, United States
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Washington University
St Louis, Missouri, 63130, United States
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Washington University School of Medicine
St Louis, Missouri, 63110, United States
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