A Study to Learn About a Clostridioides Difficile Vaccine in People 65 Years of Age and Older (BEETHOVEN)

May 22, 2026 updated by: Pfizer

A PHASE 3, PLACEBO-CONTROLLED, DOUBLE-BLINDED, RANDOMIZED STUDY TO EVALUATE THE EFFICACY, SAFETY, AND TOLERABILITY OF A CLOSTRIDIOIDES DIFFICILE VACCINE IN ADULTS 65 YEARS OF AGE AND OLDER

The purpose of the study is to learn about how effective, safe, and tolerable the Clostridioides difficile (C. difficile) vaccine is in decreasing the number of C. difficile infections (pCDI) in adults 65 years of age or older.

The participants will receive either the C. difficile vaccine or placebo (saline). A placebo does not contain any active ingredients. The vaccines will be given as a shot into the upper arm muscle.

This study looks at the number of diarrhea (loose stools) events related to a C. difficile infection, so the length of the study can change. If these events happen quickly, the study may finish sooner; if they happen slowly, it could take longer. Sometimes, the study might stop early if the vaccine clearly works or clearly doesn't. Participants will stay in the study until enough events have occurred to answer the main question. On average, each person is expected to take part for up to about three and a half years.

During this time, participants will have 3 planned clinical visits and 3 planned phone visits. After these visits, more scheduled clinic visits will happen every year until the end of study.

Besides the scheduled study visits, if at any time during the study a participant has 3 or more loose stools in 24 hours, they will be asked to save the next one (the fourth or later) and contact the study site. The study site will check to see if it could be a C. difficile infection. This check may happen at the clinic or through a phone or video call.

Study Overview

Status

Recruiting

Conditions

Clostridioides Difficile Associated Disease

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

32000

Phase

Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Name: Pfizer CT.gov Call Center
Phone Number: 1-800-718-1021
Email: ClinicalTrials.gov_Inquiries@pfizer.com

Study Locations

Argentina
- - Buenos Aires, Argentina, 1425
    - Recruiting
    - Centro Medico Barrio Parque
  - Buenos Aires, Argentina, 1039
    - Recruiting
    - Sanatorio Sagrado Corazón
  - Salta, Argentina, A4400
    - Not yet recruiting
    - Investigaciones Clinicas Salta (ICSAL)
- Buenos Aires
  - Mar del Plata, Buenos Aires, Argentina, 7600
    - Recruiting
    - Clinica Del Niño Y La Madre
- Buenos Aires F.D.
  - Buenos Aires, Buenos Aires F.D., Argentina, C1428BNF
    - Recruiting
    - Equipo Ciencia
  - Buenos Aires, Buenos Aires F.D., Argentina, 1427
    - Recruiting
    - Fundación Huésped
- Córdoba Province
  - Córdoba, Córdoba Province, Argentina, X5000IIH
    - Recruiting
    - Clinica Privada del Sol S.A
- Mendoza Province
  - Lujan de Cuyo, Mendoza Province, Argentina, 5505
    - Not yet recruiting
    - CDC Centro Médico
Japan
- Aichi-ken
  - Nagoya, Aichi-ken, Japan, 457-8511
    - Not yet recruiting
    - Kojunkai Daido Clinic
  - Nagoya, Aichi-ken, Japan, 462-0802
    - Not yet recruiting
    - Kamiiida daiichi General Hospital
- Fukuoka
  - Iizuka-shi, Fukuoka, Japan, 820-8505
    - Not yet recruiting
    - Aso Iizuka Hospital
  - Itoshima, Fukuoka, Japan, 819-1104
    - Not yet recruiting
    - Seishinkai Inoue Hospital
  - Kitakyushu-shi, Fukuoka, Japan, 806-8501
    - Not yet recruiting
    - Japan Community Healthcare Organization Kyushu Hospital
  - Onga-gun, Fukuoka, Japan, 807-0051
    - Not yet recruiting
    - Fukuoka Shinmizumaki Hospital
- Ibaraki
  - Koga, Ibaraki, Japan, 306-0041
    - Not yet recruiting
    - Koga General Hospital
- Kumamoto
  - Kumamoto, Kumamoto, Japan, 861-8520, 862-8520
    - Not yet recruiting
    - Japanese Red Cross Kumamoto Hospital
- Nagasaki
  - Ōmura, Nagasaki, Japan, 856-8562
    - Recruiting
    - National Hospital Organization Nagasaki Medical Center
- Okinawa
  - Shimajiri, Okinawa, Japan, 901-0417
    - Not yet recruiting
    - Nanbu Tokushukai Hospital
- Osaka
  - Daitō, Osaka, Japan, 547-0074
    - Not yet recruiting
    - Nozaki Tokushukai Hospital
- Tokyo
  - Chuo-ku, Tokyo, Japan, 103-0027
    - Recruiting
    - Tokyo-Eki Center-building Clinic
United Kingdom
- - Glasgow, United Kingdom, G51 4RY
    - Recruiting
    - Panthera Biopartners - Glasgow
  - Manchester, United Kingdom, M13 9WU
    - Not yet recruiting
    - Manchester Royal Infirmary
  - Manchester, United Kingdom, M15 6SE
    - Recruiting
    - Synexus Manchester Clinical Research Centre
  - Sheffield, United Kingdom, S2 5FX
    - Recruiting
    - Panthera Biopartners - Sheffield
- Cornwall
  - Newquay, Cornwall, United Kingdom, TR7 1RU
    - Recruiting
    - Newquay Health Centre
- Devon
  - Exeter, Devon, United Kingdom, EX2 5DW
    - Recruiting
    - Royal Devon & Exeter Hospital
  - Plymouth, Devon, United Kingdom, PL5 3JB
    - Recruiting
    - Knowle House Surgery
  - Torquay, Devon, United Kingdom, TQ1 4QX
    - Not yet recruiting
    - Brunel Medical Practice (St Marychurch)
- England
  - Preston, England, United Kingdom, PR2 9QB
    - Recruiting
    - Panthera Biopartners - Preston
- Glasgow CITY
  - Glasgow, Glasgow CITY, United Kingdom, ML4 3NJ
    - Not yet recruiting
    - Synexus Scotland Clinical Research Centre
- Hampshire
  - Southampton, Hampshire, United Kingdom, SO16 6YD
    - Recruiting
    - Southampton General Hospital
- Lancashire
  - Blackpool, Lancashire, United Kingdom, FY3 7EN
    - Recruiting
    - Layton Medical Centre
- Manchester
  - Rochdale, Manchester, United Kingdom, OL11 4AU
    - Recruiting
    - Panthera Biopartners - Manchester
- North Yorkshire
  - York, North Yorkshire, United Kingdom, YO24 4LJ
    - Recruiting
    - Panthera Clinic - York
- Northamptonshire
  - Corby, Northamptonshire, United Kingdom, NN17 2UR
    - Recruiting
    - Lakeside Surgery
- Northern Ireland
  - Belfast, Northern Ireland, United Kingdom, BT2 8BG
    - Recruiting
    - Ormeau Clinical Trials
- Staffordshire
  - Cheadle, Staffordshire, United Kingdom, ST10 1NS
    - Recruiting
    - Cheadle Community Hospital
- WEST Midlands
  - Birmingham, WEST Midlands, United Kingdom, B15 2SQ
    - Not yet recruiting
    - Synexus Midlands Clinical Research Centre
- Wrexham [wrecsam Gb-wrc]
  - Wrexham, Wrexham [wrecsam Gb-wrc], United Kingdom, LL13 7YP
    - Not yet recruiting
    - North Wales Clinical Research Facility
United States
- Alabama
  - Athens, Alabama, United States, 35611
    - Recruiting
    - North Alabama Research Center
  - Guntersville, Alabama, United States, 35976
    - Recruiting
    - Lakeview Clinical Research
  - Huntsville, Alabama, United States, 35801
    - Recruiting
    - Medical Affiliated Research Center
- Arizona
  - Sun City, Arizona, United States, 85351
    - Recruiting
    - Epic Medical Research-Sun City
- Arkansas
  - Little Rock, Arkansas, United States, 72205
    - Recruiting
    - Applied Research Center of Arkansas
- California
  - Daly City, California, United States, 94015
    - Recruiting
    - Kaiser Permanente Daly City
  - Los Angeles, California, United States, 90027
    - Recruiting
    - Kaiser Permanente Los Angeles Medical Center
  - Los Angeles, California, United States, 90027
    - Recruiting
    - Kaiser Permanente Oncology Pharmacy #014C
  - Mather, California, United States, 95655
    - Not yet recruiting
    - Sacramento VA Medical Center
  - Oakland, California, United States, 94611
    - Recruiting
    - Kaiser Permanente Oakland
  - Ontario, California, United States, 91761
    - Recruiting
    - Kaiser Permanente Ontario Medical Center
  - Pasadena, California, United States, 91101
    - Recruiting
    - Southern California Permanente Medical Group
  - Roseville, California, United States, 95661
    - Recruiting
    - Kaiser Permanente Roseville
  - Sacramento, California, United States, 95815
    - Recruiting
    - Kaiser Permanente Sacramento
  - Sacramento, California, United States, 95823
    - Recruiting
    - Kaiser Permanente South Sacramento
  - San Bernardino, California, United States, 92408
    - Recruiting
    - Velocity Clinical Research, San Bernardino
  - San Diego, California, United States, 92123
    - Recruiting
    - Kaiser Permanente - San Diego Medical Center
  - San Diego, California, United States, 92123
    - Recruiting
    - Kaiser Permanente Viewridge Medical Office
  - San Jose, California, United States, 95119
    - Recruiting
    - Kaiser Permanente San Jose
  - San Mateo, California, United States, 94403
    - Recruiting
    - Carbon Health - San Mateo - Hillsdale Mall
  - Santa Clara, California, United States, 95051
    - Recruiting
    - Kaiser Permanente Santa Clara
  - Toluca Lake, California, United States, 91602
    - Recruiting
    - Med Partners, Inc. dba Premiere Medical Center of Burbank, Inc.
  - Walnut Creek, California, United States, 94598
    - Recruiting
    - Diablo Clinical Research, Inc.
  - Walnut Creek, California, United States, 94596
    - Recruiting
    - Kaiser Permanente Walnut Creek
- District of Columbia
  - Washington D.C., District of Columbia, United States, 20037
    - Recruiting
    - GW Vaccine Research Unit
  - Washington D.C., District of Columbia, United States, 20037
    - Recruiting
    - The GW Medical Faculty Associates
- Florida
  - Bay Pines, Florida, United States, 33744
    - Recruiting
    - Bay Pines VA Healthcare System
  - Fort Lauderdale, Florida, United States, 33308
    - Recruiting
    - Proactive Clinical Research,LLC
  - Hialeah, Florida, United States, 33012
    - Recruiting
    - Indago Research & Health Center, Inc
  - Jacksonville, Florida, United States, 32256
    - Recruiting
    - Clinical Neuroscience Solutions, Inc. dba CNS Healthcare
  - Lake City, Florida, United States, 32055
    - Recruiting
    - M3 Wake Research - Lake City
  - Medley, Florida, United States, 33166
    - Recruiting
    - South Florida Research Organization
  - Miami, Florida, United States, 33176
    - Recruiting
    - Entrust Clinical Research
  - Miami, Florida, United States, 33130
    - Recruiting
    - Care Research Inc
  - Miami Lakes, Florida, United States, 33014
    - Recruiting
    - Charisma Medical and Research Center
  - Miami Lakes, Florida, United States, 33014
    - Recruiting
    - Palm Springs Community Health Center
  - Palmetto Bay, Florida, United States, 33157
    - Not yet recruiting
    - Innovation Medical Research Center
  - Tampa, Florida, United States, 33614
    - Recruiting
    - Angels Clinical Research Institute
- Georgia
  - Atlanta, Georgia, United States, 30303
    - Recruiting
    - Emory Steiner Building Research Center
  - Atlanta, Georgia, United States, 30303
    - Recruiting
    - Emory University Woodruff Extension Building (WEB)
  - Columbus, Georgia, United States, 31904
    - Recruiting
    - Centricity Research Columbus Georgia Multispecialty
  - Decatur, Georgia, United States, 30030
    - Recruiting
    - The Hope Clinic of Emory University
  - Savannah, Georgia, United States, 31406
    - Recruiting
    - Velocity Clinical Research, Savannah
- Illinois
  - Melrose Park, Illinois, United States, 60160
    - Recruiting
    - DM Clinical Research - Chicago
- Iowa
  - Ames, Iowa, United States, 50010
    - Recruiting
    - McFarland Clinic, PC
  - Ames, Iowa, United States, 50010
    - Recruiting
    - Accellacare - McFarland
  - Sioux City, Iowa, United States, 51106
    - Recruiting
    - Velocity Clinical Research, Sioux City
- Kansas
  - Newton, Kansas, United States, 67114
    - Recruiting
    - AMR Clinical
- Louisiana
  - Baton Rouge, Louisiana, United States, 70836
    - Recruiting
    - Ochsner Medical Complex - The Grove
  - Kenner, Louisiana, United States, 70065
    - Recruiting
    - Ochsner Clinic Foundation - Kenner Clinical Trials Unit
  - Lafayette, Louisiana, United States, 70503
    - Recruiting
    - Ochsner Lafayette General Medical Center
- Maryland
  - Baltimore, Maryland, United States, 21205
    - Not yet recruiting
    - Johns Hopkins Bloomberg School of Public Health
- Michigan
  - Southfield, Michigan, United States, 48076
    - Recruiting
    - DM Clinical Research - Detroit
  - Southfield, Michigan, United States, 48075
    - Recruiting
    - Revive Research Institute, Inc.
- Missouri
  - St Louis, Missouri, United States, 63110
    - Recruiting
    - Washington University School of Medicine
  - St Louis, Missouri, United States, 63141
    - Recruiting
    - Sundance Clinical Research
- Nebraska
  - Grand Island, Nebraska, United States, 68803
    - Recruiting
    - Velocity Clinical Research, Grand Island
  - Omaha, Nebraska, United States, 68198
    - Recruiting
    - University of Nebraska Medical Center
  - Omaha, Nebraska, United States, 68105
    - Recruiting
    - University of Nebraska Medical Center
  - Omaha, Nebraska, United States, 68134
    - Recruiting
    - Velocity Clinical Research, Omaha
- Nevada
  - Reno, Nevada, United States, 89502
    - Recruiting
    - Renown Regional Medical Center
  - Reno, Nevada, United States, 89502
    - Recruiting
    - Renown Center for Advanced Medicine
  - Reno, Nevada, United States, 89519
    - Recruiting
    - University Health
- New Jersey
  - Hackensack, New Jersey, United States, 07601
    - Recruiting
    - HMH Hackensack University Medical Center
  - Hackensack, New Jersey, United States, 07601
    - Recruiting
    - Hackensack Meridian Health Hackensack University Medical Center
  - Hackensack, New Jersey, United States, 07601
    - Recruiting
    - HMH David Jurist Research Building
  - Neptune City, New Jersey, United States, 07753
    - Recruiting
    - Hackensack Meridian Jersey Shore University Medical Center
  - Neptune City, New Jersey, United States, 07753
    - Recruiting
    - HOPE Tower at Jersey Shore University Medical Center
  - New Brunswick, New Jersey, United States, 08901
    - Not yet recruiting
    - Rutgers Robert Wood Johnson Medical School
  - Somers Point, New Jersey, United States, 08244
    - Recruiting
    - South Jersey Infectious Disease
- New Mexico
  - Albuquerque, New Mexico, United States, 87102
    - Recruiting
    - Albuquerque Clinical Trials, Inc.
- New York
  - Brooklyn, New York, United States, 11220
    - Recruiting
    - NYU Langone Health
  - East Syracuse, New York, United States, 13057
    - Recruiting
    - Upstate Global Health Institute
  - Long Island City, New York, United States, 11102
    - Recruiting
    - Mount Sinai Queens
  - Manhasset, New York, United States, 11030
    - Recruiting
    - North Shore University Hospital
  - Manhasset, New York, United States, 11030
    - Recruiting
    - Northwell Health Infectious Disease
  - Mineola, New York, United States, 11501
    - Recruiting
    - NYU Langone Health
  - Mount Kisco, New York, United States, 10549
    - Recruiting
    - Northern Westchester Hospital
  - New York, New York, United States, 10016
    - Recruiting
    - NYU Langone Health
  - New York, New York, United States, 10032
    - Recruiting
    - Columbia University Irving Medical Center
  - New York, New York, United States, 10029
    - Recruiting
    - Icahn School Of Medicine At Mount Sinai
  - New York, New York, United States, 10019
    - Recruiting
    - Mount Sinai West
  - New York, New York, United States, 10025
    - Recruiting
    - Mount Sinai Morningside
  - Rochester, New York, United States, 14609
    - Recruiting
    - Rochester Clinical Research, LLC
  - Sleepy Hollow, New York, United States, 10591
    - Recruiting
    - Phelps Hospital Geriatric Medicine & Improvement Science
  - The Bronx, New York, United States, 10467
    - Recruiting
    - Montefiore Medical Center
  - The Bronx, New York, United States, 10468
    - Not yet recruiting
    - James J. Peters VA Medical Center
- North Carolina
  - Cary, North Carolina, United States, 27518
    - Recruiting
    - Accellacare - Cary
  - Durham, North Carolina, United States, 27703
    - Recruiting
    - Duke Vaccine and Trials Unit
  - Greensboro, North Carolina, United States, 27405
    - Recruiting
    - Medication Management
  - Hickory, North Carolina, United States, 28601
    - Recruiting
    - Accellacare - Hickory
  - High Point, North Carolina, United States, 27262
    - Recruiting
    - Atrium Health Wake Forest Baptist Infectious Disease-High Point
  - Raleigh, North Carolina, United States, 27609
    - Recruiting
    - Accellacare - Raleigh
  - Raleigh, North Carolina, United States, 27609
    - Recruiting
    - Duke University Health System
  - Raleigh, North Carolina, United States, 27609
    - Recruiting
    - Raleigh Medical Group P.A.
  - Salisbury, North Carolina, United States, 28144
    - Recruiting
    - Accellacare - Salisbury
  - Wilmington, North Carolina, United States, 28401
    - Recruiting
    - Accellacare - Wilmington
  - Wilmington, North Carolina, United States, 28401
    - Recruiting
    - Wilmington Health, PLLC
  - Winston-Salem, North Carolina, United States, 27157
    - Recruiting
    - Wake Forest Baptist Health
  - Winston-Salem, North Carolina, United States, 27103
    - Recruiting
    - Accellacare - Winston-Salem
- Ohio
  - Cincinnati, Ohio, United States, 45212
    - Recruiting
    - CTI Clinical Research Center
  - Cleveland, Ohio, United States, 44106
    - Recruiting
    - VA Northeast Ohio Healthcare System Louis Stokes Cleveland VA Medical Center
- Oregon
  - Portland, Oregon, United States, 97227
    - Recruiting
    - Kaiser Permanente Center for Health Research
- Pennsylvania
  - Camp Hill, Pennsylvania, United States, 17011
    - Recruiting
    - Capital Area Research, LLC
  - Philadelphia, Pennsylvania, United States, 19107
    - Recruiting
    - DM Clinical Research - Philadelphia
- South Carolina
  - Little River, South Carolina, United States, 29566
    - Recruiting
    - Walker Family Care
  - Myrtle Beach, South Carolina, United States, 29572
    - Recruiting
    - Trial Management Associates
  - Myrtle Beach, South Carolina, United States, 29572
    - Recruiting
    - Trial Management Associates, LLC
  - Spartanburg, South Carolina, United States, 29303
    - Recruiting
    - Velocity Clinical Research, Spartanburg
- Tennessee
  - Knoxville, Tennessee, United States, 37909
    - Recruiting
    - New Phase Research and Development
  - Memphis, Tennessee, United States, 38119
    - Recruiting
    - Clinical Neuroscience Solutions Inc.
  - Nashville, Tennessee, United States, 37232
    - Not yet recruiting
    - Vanderbilt University Medical Center
  - Nashville, Tennessee, United States, 37232
    - Not yet recruiting
    - Vanderbilt Vaccine Research Program
  - Nashville, Tennessee, United States, 37212
    - Not yet recruiting
    - The Vanderbilt Vaccine Research Program Clinic at The Village at Vanderbilt
  - Nashville, Tennessee, United States, 37232
    - Not yet recruiting
    - Vanderbilt Investigational Drug Service (IDS)
  - Nashville, Tennessee, United States, 37232
    - Not yet recruiting
    - Vanderbilt Vaccine Research Program Laboratory
- Texas
  - Dallas, Texas, United States, 75246
    - Recruiting
    - North Texas Infectious Diseases Consultants, P.A
  - Dallas, Texas, United States, 75237
    - Recruiting
    - Family Health Watch - KeyPoint Clinical Research
  - Dallas, Texas, United States, 75240
    - Recruiting
    - KeyPoint Clinical Research
  - Euless, Texas, United States, 76040
    - Recruiting
    - Cedar Health Research - Euless
  - Houston, Texas, United States, 77030
    - Recruiting
    - Baylor College of Medicine
  - Houston, Texas, United States, 77030
    - Not yet recruiting
    - The University of Texas Health Science Center at Houston
  - Houston, Texas, United States, 77065
    - Recruiting
    - DM Clinical Research- Cyfair
  - Houston, Texas, United States, 77087
    - Recruiting
    - Mercury Clinical Research - Santa Clara Family Clinic
  - Houston, Texas, United States, 77030
    - Not yet recruiting
    - UT Physicians
  - Houston, Texas, United States, 77030
    - Not yet recruiting
    - Memorial Hermann Hospital - TMC
  - Tomball, Texas, United States, 77375
    - Recruiting
    - Northwest Houston Heart Center
  - Tomball, Texas, United States, 77375
    - Recruiting
    - Dynamed Clinical Research, LP d/b/a DM Clinical Research
- Utah
  - Salt Lake City, Utah, United States, 84121
    - Recruiting
    - J. Lewis Research, Inc. / Foothill Family Clinic South
- Vermont
  - Burlington, Vermont, United States, 05401
    - Recruiting
    - The University of Vermont Medical Center Inc.
  - Burlington, Vermont, United States, 05401
    - Recruiting
    - UVM Larner College of Medicine MMG/VCT
- Virginia
  - Richmond, Virginia, United States, 23226
    - Recruiting
    - Clinical Research Partners, LLC
- Washington
  - Everett, Washington, United States, 98201
    - Recruiting
    - Providence Regional Medical Center Everett
  - Seattle, Washington, United States, 98104
    - Recruiting
    - University of Washington - Harborview Medical Center
  - Seattle, Washington, United States, 98101
    - Recruiting
    - Kaiser Permanente Washington Health Research Institute (KPWHRI)

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

Older Adult

Accepts Healthy Volunteers

Yes

Description

Who Can Join the Study (Inclusion Criteria):

• People with recent or future planned contact with healthcare systems or who have recently received antibiotics.

Who Cannot Join the Study (Exclusion Criteria):

Anyone who has had CDI before.
Anyone who has had surgery to remove part of their small or large intestine.
Anyone who often has diarrhea (meaning three or more loose stools in a day, more than once a month).
Anyone who has already received a vaccine or special antibody treatment for C. difficile.
Anyone who has had a serious allergic reaction to a vaccine or to any part of the study vaccines.
Anyone who might not respond well to the vaccine because their immune system is weak (either from a disease or from treatment).
Anyone with cancer that has spread, kidney failure, or another serious health problem.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Primary Purpose: Prevention
Allocation: Randomized
Interventional Model: Parallel Assignment
Masking: Triple

Number of Arms

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: C.difficile vaccine Novel vaccine formulation	Biological: C.difficile vaccine C.difficile vaccine given as an intramuscular injection
Other: Saline Placebo	Other: Saline Placebo 0.9% sodium chloride solution given as a intramuscular injection

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The percentage of participants reporting local reactions Time Frame: For 7 days after each vaccination	Injection site pain, redness, and swelling as self-reported in electronic diaries	For 7 days after each vaccination
The percentage of participants reporting systemic events Time Frame: For 7 days after each vaccination	Fever, vomiting, fatigue, headache, muscle pain, and joint pain as self-reported in electronic diaries	For 7 days after each vaccination
Percentage of participants reporting adverse events Time Frame: From each vaccination through 1 month after each vaccination	As elicited by investigator site staff	From each vaccination through 1 month after each vaccination
Percentage of participants reporting serious adverse events Time Frame: From Vaccination 1 (Day 1) through 12 months after Vaccination 2 (last dose) (18 months)	As elicited by investigator site staff	From Vaccination 1 (Day 1) through 12 months after Vaccination 2 (last dose) (18 months)
The incidence of the first episode of medically attended and clinically meaningful primary Clostridioides difficile infection (CDI) Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	First episode of medically attended and clinically meaningful primary CDI incidence per 1000 person- years of follow- up	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)
The incidence of the first episode of medically attended primary CDI Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	First episode of medically attended primary CDI incidence per 1000 person- years of follow- up	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)
The incidence of the first episode of clinically meaningful primary CDI Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	First episode of clinically meaningful primary CDI incidence per 1000 person- years of follow- up	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The incidence of antibiotic use in the treatment of a first episode of the primary CDI Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	First episode of primary CDI with antibiotic use incidence per 1000 person- years of follow- up	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)
The incidence of severe primary CDI as defined by Infectious Diseases Society of America (IDSA)/ Society for Healthcare Epidemiology of America (SHEA) Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	First episode of severe or fulminant primary CDI incidence per 1000 person- years of follow- up	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)
The incidence of a first episode of primary CDI (any severity) Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	First episode of primary CDI incidence per 1000 person- years of follow- up	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)
The incidence of all CDI (primary and recurrent) Time Frame: from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)	Time to all C.difficile infection cases	from 14 days after Vaccination 2 to the end of the surveillance period (up to approximately 3.5 years)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Pfizer

Investigators

Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

To obtain contact information for a study center near you, click here.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 10, 2025

Primary Completion (Estimated)

December 11, 2028

Study Completion (Estimated)

June 7, 2029

Study Registration Dates

First Submitted

December 5, 2025

First Submitted That Met QC Criteria

December 5, 2025

First Posted (Actual)

December 15, 2025

Study Record Updates

Last Update Posted (Actual)

May 26, 2026

Last Update Submitted That Met QC Criteria

May 22, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

C4771002

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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A PHASE 3, PLACEBO-CONTROLLED, DOUBLE-BLINDED, RANDOMIZED STUDY TO EVALUATE THE EFFICACY, SAFETY, AND TOLERABILITY OF A CLOSTRIDIOIDES DIFFICILE VACCINE IN ADULTS 65 YEARS OF AGE AND OLDER

Study Overview

Status

Conditions

Intervention / Treatment

Study Type

Enrollment (Estimated)

Phase

Contacts and Locations

Study Contact

Study Locations

Participation Criteria

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Ages Eligible for Study

Accepts Healthy Volunteers

Description

Study Plan

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Design Details

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Participant Group / Arm

Intervention / Treatment

What is the study measuring?

Primary Outcome Measures

Outcome Measure

Measure Description

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Secondary Outcome Measures

Outcome Measure

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First Submitted

First Submitted That Met QC Criteria

First Posted (Actual)

Study Record Updates

Last Update Posted (Actual)

Last Update Submitted That Met QC Criteria

Last Verified

More Information

Terms related to this study

Other Study ID Numbers

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

IPD Plan Description

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Studies a U.S. FDA-regulated device product

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