Clostridium Difficile Associated DiseasePhase 3NCT03918629

Clostridium Difficile Vaccine 2-Dose Versus 3-Dose Study

A Phase 3 study testing Clostridium difficile in people with Clostridium Difficile Associated Disease, run by Pfizer at 52 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record

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Trial summary

Who is it for?: Ages 50 years and olderHealthy volunteers can take part
Conditions the study is for: Clostridium Difficile Associated Disease
What is being tested?: Clostridium difficile
Type of treatment: Vaccines
Could I receive a placebo?: Yes, some participants may receive a placebo
How many people: 1,994 participants
Where: 52 sitesUnited States
Study dates: 1 Apr 2019to 22 Dec 2020
Phase: Phase 3
Are there results?: Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 50 years and older
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Evidence of a personally signed and dated informed consent document.
Willing and able to comply with study procedures.
Subjects with an increased risk of future contact with healthcare systems or subjects who have received systemic antibiotics in the previous 12 weeks.
Ability to be contacted by telephone during study participation.

Who cannot join

Pregnant female participants; breastfeeding female participants; positive urine pregnancy test for women of childbearing potential (WOCBP); and WOCBP who are, in the opinion of the investigator, sexually active and at risk for pregnancy and are unwilling or unable to use effective methods of contraception as outlined in this protocol from the signing of the informed consent until at least 28 days after the last dose of investigational product.
Prior episode of CDI, confirmed by either laboratory test or diagnosis of pseudomembranous colitis at colonoscopy, at surgery, or histopathologically.
Participants who may be unable to respond to vaccination due to:
Metastatic malignancy; or
End-stage renal disease (glomerular filtration rate <15 mL/min/1.73 m2 or on dialysis).
Any serious medical disorder that in the investigator's opinion is likely to be fatal within the next 12 months.

Show all 17Show fewer

Congenital or acquired immunodeficiency.
Known infection with human immunodeficiency virus (HIV).
Any bleeding disorder or anticoagulant therapy that would contraindicate IM injection.
Any contraindication to vaccination or vaccine components, including previous anaphylactic reaction to any vaccine or vaccine-related components.
Other acute or chronic medical or psychiatric condition including recent (within the past year) or active suicidal ideation or behavior 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 and, in the judgment of the investigator, would make the participant inappropriate for entry into this study.
Previous administration of an investigational C difficile vaccine or C difficile mAb therapy.
Receipt of systemic corticosteroids for greater than or equal to 14 days within 28 days before enrollment.
Receipt of chronic systemic treatment with other known immunosuppressant medications, or radiotherapy, within 6 months before enrollment.
Receipt of blood products or immunoglobulins within 6 months before enrollment.
Participation in other studies involving investigational drug(s)/vaccine(s) within 28 days prior to study entry until 1 month after the third vaccination.
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 Pfizer employees, including their family members, directly involved in the conduct of the study.

Trial locations and contacts

52 sites in 1 country.

City, postcode or hospital

52 sites in 1 country

United States52 sites

North Alabama Research Center, LLC
Athens, Alabama, 35611
ARC Clinical Research at Wilson Parke
Austin, Texas, 78726
Bellaire Doctor's Clinic
Bellaire, Texas, 77401
Holston Medical Group
Bristol, Tennessee, 37620
East Valley Gastroenterology and Hepatology Associates
Chandler, Arizona, 85224
PMG Research of Charlotte LLC
Charlotte, North Carolina, 28209
Clinical Research Professionals Inc.
Chesterfield, Missouri, 63005
Innovative Research of West Florida, Inc.
Clearwater, Florida, 33756
Aventiv Research Inc.
Columbus, Ohio, 43213
PriMed Clinical Research
Dayton, Ohio, 45419
Accel Research Sites - DeLand Clinical Research Unit
DeLand, Florida, 32720
J. Lewis Research Inc. / Foothill Family Clinic Draper
Draper, Utah, 84020
Lillestol Research LLC
Fargo, North Dakota, 58104
Texas Health Care, PLLC
Fort Worth, Texas, 76104
Ventavia Research Group, LLC
Fort Worth, Texas, 76104
Medical Research South
Goose Creek, South Carolina, 29445
PharmQuest
Greensboro, North Carolina, 27408
MedPharmics, LLC
Gulfport, Mississippi, 39503
Accellacare - Hickory
Hickory, North Carolina, 28601
Texas Center for Drug Development, Inc.
Houston, Texas, 77081
Medical Affiliated Research Center
Huntsville, Alabama, 35801
Snake River Research, PLLC
Idaho Falls, Idaho, 83404
Paradigm Clinical Research Centers, Inc.
La Mesa, California, 91942
Main Street Physician's Care - Waterway
Little River, South Carolina, 29566
MedPharmics, LLC
Metairie, Louisiana, 70006
Acevedo Clinical Research Associates
Miami, Florida, 33142
Virginia Research Center LLC
Midlothian, Virginia, 23114
MOC Research
Mishawaka, Indiana, 46544
Coastal Carolina Research Center
North Charleston, South Carolina, 29405
Clinical Neuroscience Solutions, Inc.
Orlando, Florida, 32801
Clinical Neuroscience Solutions, Inc.
Orlando, Florida, 32806
Pines Care Research Center, LLC
Pembroke Pines, Florida, 33026
The Pain Center of Arizona
Peoria, Arizona, 85381
HOPE Research Institute
Phoenix, Arizona, 85018
The Pain Center of Arizona
Phoenix, Arizona, 85018
The Pain Center of Arizona
Phoenix, Arizona, 85032
Progressive Medical Research
Port Orange, Florida, 32127
PMG Research of Raleigh
Raleigh, North Carolina, 27609
Amici Clinical Research
Raritan, New Jersey, 08869
Paradigm Clinical Research Centers, Inc.
Redding, California, 96001
Rochester Clinical Research, Inc
Rochester, New York, 14609
J. Lewis Research, Inc. / Foothill Family Clinic
Salt Lake City, Utah, 84109
J. Lewis Research, Inc. / Foothill Family Clinic South
Salt Lake City, Utah, 84121
Diagnostics Research Group
San Antonio, Texas, 78229
Meridian Clinical Research, LLC
Savannah, Georgia, 31406
J. Lewis Research, Inc. / Jordan River Family Medicine
South Jordan, Utah, 84095
DM Clinical Research
Tomball, Texas, 77375
Martin Diagnostic Clinic
Tomball, Texas, 77375
Wenatchee Valley Hospital & Clinics
Wenatchee, Washington, 98801
Paradigm Research
Wheat Ridge, Colorado, 80033
PMG Research of Wilmington, LLC
Wilmington, North Carolina, 28401
PMG Research of Winston-Salem, LLC
Winston-Salem, North Carolina, 27103

Other trials in United States

About this study

Official title: A PHASE 3, RANDOMIZED OBSERVER-BLINDED STUDY TO EVALUATE THE IMMUNOGENICITY, SAFETY, AND TOLERABILITY OF 2 DOSES COMPARED TO 3 DOSES OF CLOSTRIDIUM DIFFICILE VACCINE IN ADULTS 50 YEARS OF AGE AND OLDER

This study will investigate a Clostridium difficile vaccine in adults 50 years of age and older. In half the adults, all 3 doses given are the Clostridium difficile vaccine, and in half the adults, 2 of the 3 doses are the Clostridium difficile vaccine with the other dose containing no active ingredients. The study will look at the subjects' immune response to the vaccine and assess the safety and tolerability of a 2-dose regimen of Clostridium difficile vaccine compared to a 3-dose regimen of Clostridium difficile vaccine.

Read the detailed description

Serology for B5091019 will be forthcoming. There have been delays due to discussions with the FDA on statistical analysis as well as delays attributable to the COVID pandemic.

Conditions: Clostridium Difficile Associated Disease
Being tested: Clostridium difficile, Placebo
Keywords: Clostridium Difficile, vaccine

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

Clostridium difficileBiological
Toxoid-based Clostridium difficile vaccine
PlaceboBiological
Normal saline solution (0.9% sodium chloride)

Study groups in NCT03918629
Study group	Role	What they receive
Clostridium difficile vaccine - 3 dose	Experimental	All 3 doses are the Clostridium difficile vaccine Receives: Biological: Clostridium difficile
Clostridium difficile vaccine - 2 dose	Experimental	2 of the 3 doses are the Clostridium difficile vaccine with the other being placebo Receives: Biological: Clostridium difficile; Biological: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

Adjusted Geometric Mean Concentration (GMC) of Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibodies at Month 7 for Evaluable Immunogenicity Population (EIP)
Adjusted GMCs and 2-sided 95% confidence intervals (CIs) of toxin A and toxin B specific neutralizing antibody levels were calculated by exponentiating the least square (LS) means and the corresponding CIs based on analysis of logarithmically transformed concentrations using a linear regression model with terms of baseline concentration (log scale) and vaccine group. EIP at Month 7 (EI7): all enrolled participants who received all 3 doses of investigational product; had blood drawn for assay testing within 28 to 47 days after visit 4; had valid and determinate assay results for either toxin A or B for the specified analysis at Month 7; had no major protocol deviations.
Measured: Month 7
Percentage of Participants Achieving Seroresponse for Clostridium Difficile Toxin A and Toxin B at Month 7 for EIP
Seroresponse was defined as at least a 4-fold rise from the baseline neutralizing antibody level following vaccination. 95% CI was based on Clopper-Pearson method. EI7: all enrolled participants who received all 3 doses of investigational product; had blood drawn for assay testing within 28 to 47 days after visit 4; had valid and determinate assay results for either toxin A or B for the specified analysis at Month 7; had no major protocol deviations.
Measured: Month 7
Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 1
Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an electronic diary (e-diary). Redness and swelling were measured and recorded in measuring device units, where 1 measuring device unit= 0.5 centimeter (cm). Redness and swelling were graded as mild: 2.5-5.0 cm, moderate: greater than (>) 5.0-10.0 cm, severe: >10.0 cm, potentially life threatening: necrosis or exfoliative dermatitis for redness, or necrosis for swelling. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, potentially life threatening: emergency room visit or hospitalization. The maximum severity was defined as highest grading of each local reaction through 7 days of vaccination.
Measured: Up to 7 days after Dose 1 of investigational product at Month 0
Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 2
Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an e-diary. Redness and swelling were measured and recorded in measuring device units, where 1 measuring device unit= 0.5 cm. Redness and swelling were graded as mild: 2.5-5.0 cm, moderate: >5.0-10.0 cm, severe: >10.0 cm, potentially life threatening: necrosis or exfoliative dermatitis for redness, or necrosis for swelling. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, potentially life threatening: emergency room visit or hospitalization. The maximum severity was defined as highest grading of each local reaction through 7 days of vaccination.
Measured: Up to 7 days after Dose 2 of investigational product at Month 1
Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 3
Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an e-diary. Redness and swelling were measured and recorded in measuring device units, where 1 measuring device unit= 0.5 cm. Redness and swelling were graded as mild: 2.5-5.0 cm, moderate: >5.0-10.0 cm, severe: >10.0 cm, potentially life threatening: necrosis or exfoliative dermatitis for redness, or necrosis for swelling. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, potentially life threatening: emergency room visit or hospitalization. The maximum severity was defined as highest grading of each local reaction through 7 days of vaccination.
Measured: Up to 7 days after Dose 3 of investigational product at Month 6
Percentage of Participants With Systemic Events by Maximum Severity Through 7 Days After Dose 1
Systemic events included fever, fatigue, headache, joint pain, muscle pain and vomiting. These were recorded by participants in an e-diary. Fever was categorized as: mild (38.0 to 38.4 degree [deg] Celsius [C]), moderate (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C) and potentially life threatening (>40.0 deg C). Fatigue, headache, muscle pain and joint pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily routine activity and potentially life threatening: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours(h), moderate: >2 times in 24h, severe: required intravenous hydration and potentially life threatening: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event through 7 days of vaccination.
Measured: Up to 7 days after Dose 1 of investigational product at Month 0
Percentage of Participants With Systemic Events by Maximum Severity Through 7 Days After Dose 2
Systemic events included fever, fatigue, headache, joint pain, muscle pain and vomiting. These were recorded by participants in an e-diary. Fever was categorized as: mild (38.0 to 38.4 deg C), moderate (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C) and potentially life threatening (>40.0 deg C). Fatigue, headache, muscle pain and joint pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily routine activity and potentially life threatening: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24h, moderate: >2 times in 24h, severe: required intravenous hydration and potentially life threatening: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event through 7 days of vaccination.
Measured: Up to 7 days after Dose 2 of investigational product at Month 1
Percentage of Participants With Systemic Events by Maximum Severity Through 7 Days After Dose 3
Systemic events included fever, fatigue, headache, joint pain, muscle pain and vomiting. These were recorded by participants in an e-diary. Fever was categorized as: mild (38.0 to 38.4 deg C), moderate (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C) and potentially life threatening (>40.0 deg C). Fatigue, headache, muscle pain and joint pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily routine activity and potentially life threatening: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24h, moderate: >2 times in 24h, severe: required intravenous hydration and potentially life threatening: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event through 7 days of vaccination.
Measured: Up to 7 days after Dose 3 of investigational product at Month 6
Percentage of Participants With Adverse Events Through 1 Month After Last Study Vaccination
An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Percentage of participants with any AEs (both serious and all non-serious AEs) and non-serious AEs through 1 month after last study vaccination were reported in this outcome measure. Only AEs and non-SAEs collected by non-systematic assessment (i.e., excluding local reactions and systemic events) were reported in this outcome measure.
Measured: From day of first dose up to 1 month after last dose (up to Month 7)
Percentage of Participants With Serious Adverse Events (SAEs) Through 6 Months After Last Study Vaccination
SAE was any untoward medical occurrence that at any dose resulted in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly.
Measured: From day of first dose up to 6 months after last dose (up to Month 12)

Secondary outcomes (2)

Adjusted Geometric Mean Concentration for Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibody at Month 12 for EIP
Adjusted GMCs and 2-sided 95% CIs of toxin A and toxin B specific neutralizing antibody levels were calculated by exponentiating the LS means and the corresponding CIs based on analysis of logarithmically transformed concentrations using a linear regression model with terms of baseline concentration (log scale) and vaccine group. EI12: all enrolled participants who received all 3 doses of investigational product; had blood drawn for assay testing within 165 to 200 days after visit 4; had valid and determinate assay results for either toxin A or B for the specified analysis at Month 12; had no major protocol deviations.
Measured: Month 12
Percentage of Participants Achieving Seroresponse for Clostridium Difficile Toxin A and Toxin B at Month 12 for EIP
Seroresponse was defined as at least a 4-fold rise from the baseline neutralizing antibody following vaccination. 95% CI was based on Clopper-Pearson method. EI12: all enrolled participants who received all 3 doses of investigational product; had blood drawn for assay testing within 165 to 200 days after visit 4; had valid and determinate assay results for either toxin A or B for the specified analysis at Month 12; had no major protocol deviations.
Measured: Month 12

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

1 Apr 201922 Dec 2020

First posted17 Apr 2019
Study start1 Apr 2019
Primary completion22 Dec 2020
Study completion22 Dec 2020

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Other trials for Clostridium Difficile Associated DiseaseStudies of the same condition, open and under way.
More trials run by PfizerThe sponsor's other registered studies.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 3
Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Triple blind
Who is masked: Participant, Investigator, Outcomes assessor
Enrolment: 1,994 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT03918629
Sponsor's protocol ID: B5091019
Status last verified: Dec 2023
First submitted: 2 Apr 2019
Last updated: 10 Jan 2024
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: 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.

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

See locations

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Role of Bile Acids and Microbiota in Clostridioides Difficile Infection in Ulcerative Colitis
Ulcerative Colitis
RecruitingPhase 2/3
Secondary Prevention of Clostridioides Difficile Using Vancomycin
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All Clostridium Difficile Associated Disease trials

Study at a glance

From the registry record, last updated by the sponsor on 10 Jan 2024. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A PHASE 3, RANDOMIZED OBSERVER-BLINDED STUDY TO EVALUATE THE IMMUNOGENICITY, SAFETY, AND TOLERABILITY OF 2 DOSES COMPARED TO 3 DOSES OF CLOSTRIDIUM DIFFICILE VACCINE IN ADULTS 50 YEARS OF AGE AND OLDER
ClinicalTrials.gov ID: NCT03918629
Acronym / sponsor ID: B5091019
Conditions: Clostridium Difficile Associated Disease
Keywords: Clostridium Difficile, vaccine
Phase: Phase 3
Study type: Interventional
Recruitment status: Completed
Enrolment: 1,994 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Study start: 1 Apr 2019 (actual)
Primary completion: 22 Dec 2020 (actual)
Study completion: 22 Dec 2020 (actual)
First posted: 17 Apr 2019 (actual)
Results: Posted 10 Jan 2024

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Detailed description

Serology for B5091019 will be forthcoming. There have been delays due to discussions with the FDA on statistical analysis as well as delays attributable to the COVID pandemic.

Study design

Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Triple blind (participant, investigator, outcomes assessor)
Number of arms: 2

Arm	Type	Receives
Clostridium difficile vaccine - 3 dose	Experimental	Biological: Clostridium difficileAll 3 doses are the Clostridium difficile vaccine
Clostridium difficile vaccine - 2 dose	Experimental	Biological: Clostridium difficile, Biological: Placebo2 of the 3 doses are the Clostridium difficile vaccine with the other being placebo

Who may qualify

Ages: 50 years and older
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (4 listed)

Evidence of a personally signed and dated informed consent document.
Willing and able to comply with study procedures.
Subjects with an increased risk of future contact with healthcare systems or subjects who have received systemic antibiotics in the previous 12 weeks.
Ability to be contacted by telephone during study participation.

Key exclusion criteria (17 listed)

Pregnant female participants; breastfeeding female participants; positive urine pregnancy test for women of childbearing potential (WOCBP); and WOCBP who are, in the opinion of the investigator, sexually active and at risk for pregnancy and are unwilling or unable to use effective methods of contraception as outlined in this protocol from the signing of the informed consent until at least 28 days after the last dose of investigational product.
Prior episode of CDI, confirmed by either laboratory test or diagnosis of pseudomembranous colitis at colonoscopy, at surgery, or histopathologically.
Participants who may be unable to respond to vaccination due to:
Known infection with human immunodeficiency virus (HIV).
Any bleeding disorder or anticoagulant therapy that would contraindicate IM injection.

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
Clostridium difficileToxoid-based Clostridium difficile vaccine	Biological	Clostridium difficile vaccine - 2 dose, Clostridium difficile vaccine - 3 dose
PlaceboNormal saline solution (0.9% sodium chloride)	Biological	Clostridium difficile vaccine - 2 dose

Primary outcome

Adjusted Geometric Mean Concentration (GMC) of Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibodies at Month 7 for Evaluable Immunogenicity Population (EIP)
Time frame: Month 7
Adjusted GMCs and 2-sided 95% confidence intervals (CIs) of toxin A and toxin B specific neutralizing antibody levels were calculated by exponentiating the least square (LS) means and the corresponding CIs based on analysis of logarithmically transformed concentrations using a linear regression model with terms of baseline concentration (log scale) and vaccine group. EIP at Month 7 (EI7): all enrolled participants who received all 3 doses of investigational product; had blood drawn for assay testing within 28 to 47 days after visit 4; had valid and determinate assay results for either toxin A or B for the specified analysis at Month 7; had no major protocol deviations.
Percentage of Participants Achieving Seroresponse for Clostridium Difficile Toxin A and Toxin B at Month 7 for EIP
Time frame: Month 7
Seroresponse was defined as at least a 4-fold rise from the baseline neutralizing antibody level following vaccination. 95% CI was based on Clopper-Pearson method. EI7: all enrolled participants who received all 3 doses of investigational product; had blood drawn for assay testing within 28 to 47 days after visit 4; had valid and determinate assay results for either toxin A or B for the specified analysis at Month 7; had no major protocol deviations.
Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 1
Time frame: Up to 7 days after Dose 1 of investigational product at Month 0
Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an electronic diary (e-diary). Redness and swelling were measured and recorded in measuring device units, where 1 measuring device unit= 0.5 centimeter (cm). Redness and swelling were graded as mild: 2.5-5.0 cm, moderate: greater than (>) 5.0-10.0 cm, severe: >10.0 cm, potentially life threatening: necrosis or exfoliative dermatitis for redness, or necrosis for swelling. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, potentially life threatening: emergency room visit or hospitalization. The maximum severity was defined as highest grading of each local reaction through 7 days of vaccination.
Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 2
Time frame: Up to 7 days after Dose 2 of investigational product at Month 1
Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an e-diary. Redness and swelling were measured and recorded in measuring device units, where 1 measuring device unit= 0.5 cm. Redness and swelling were graded as mild: 2.5-5.0 cm, moderate: >5.0-10.0 cm, severe: >10.0 cm, potentially life threatening: necrosis or exfoliative dermatitis for redness, or necrosis for swelling. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, potentially life threatening: emergency room visit or hospitalization. The maximum severity was defined as highest grading of each local reaction through 7 days of vaccination.
Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 3
Time frame: Up to 7 days after Dose 3 of investigational product at Month 6
Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an e-diary. Redness and swelling were measured and recorded in measuring device units, where 1 measuring device unit= 0.5 cm. Redness and swelling were graded as mild: 2.5-5.0 cm, moderate: >5.0-10.0 cm, severe: >10.0 cm, potentially life threatening: necrosis or exfoliative dermatitis for redness, or necrosis for swelling. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, potentially life threatening: emergency room visit or hospitalization. The maximum severity was defined as highest grading of each local reaction through 7 days of vaccination.
Percentage of Participants With Systemic Events by Maximum Severity Through 7 Days After Dose 1
Time frame: Up to 7 days after Dose 1 of investigational product at Month 0
Systemic events included fever, fatigue, headache, joint pain, muscle pain and vomiting. These were recorded by participants in an e-diary. Fever was categorized as: mild (38.0 to 38.4 degree [deg] Celsius [C]), moderate (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C) and potentially life threatening (>40.0 deg C). Fatigue, headache, muscle pain and joint pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily routine activity and potentially life threatening: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours(h), moderate: >2 times in 24h, severe: required intravenous hydration and potentially life threatening: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event through 7 days of vaccination.
Percentage of Participants With Systemic Events by Maximum Severity Through 7 Days After Dose 2
Time frame: Up to 7 days after Dose 2 of investigational product at Month 1
Systemic events included fever, fatigue, headache, joint pain, muscle pain and vomiting. These were recorded by participants in an e-diary. Fever was categorized as: mild (38.0 to 38.4 deg C), moderate (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C) and potentially life threatening (>40.0 deg C). Fatigue, headache, muscle pain and joint pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily routine activity and potentially life threatening: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24h, moderate: >2 times in 24h, severe: required intravenous hydration and potentially life threatening: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event through 7 days of vaccination.
Percentage of Participants With Systemic Events by Maximum Severity Through 7 Days After Dose 3
Time frame: Up to 7 days after Dose 3 of investigational product at Month 6
Systemic events included fever, fatigue, headache, joint pain, muscle pain and vomiting. These were recorded by participants in an e-diary. Fever was categorized as: mild (38.0 to 38.4 deg C), moderate (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C) and potentially life threatening (>40.0 deg C). Fatigue, headache, muscle pain and joint pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily routine activity and potentially life threatening: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24h, moderate: >2 times in 24h, severe: required intravenous hydration and potentially life threatening: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event through 7 days of vaccination.
Percentage of Participants With Adverse Events Through 1 Month After Last Study Vaccination
Time frame: From day of first dose up to 1 month after last dose (up to Month 7)
An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Percentage of participants with any AEs (both serious and all non-serious AEs) and non-serious AEs through 1 month after last study vaccination were reported in this outcome measure. Only AEs and non-SAEs collected by non-systematic assessment (i.e., excluding local reactions and systemic events) were reported in this outcome measure.
Percentage of Participants With Serious Adverse Events (SAEs) Through 6 Months After Last Study Vaccination
Time frame: From day of first dose up to 6 months after last dose (up to Month 12)
SAE was any untoward medical occurrence that at any dose resulted in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly.

2 secondary outcomes

Adjusted Geometric Mean Concentration for Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibody at Month 12 for EIP
Time frame: Month 12
Percentage of Participants Achieving Seroresponse for Clostridium Difficile Toxin A and Toxin B at Month 12 for EIP
Time frame: Month 12

Results and safety

Results posted to the registry on 10 Jan 2024, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
2-Dose Clostridium Difficile Vaccine	996	863
3-Dose Clostridium Difficile Vaccine	998	880

Primary outcome: Adjusted Geometric Mean Concentration (GMC) of Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibodies at Month 7 for Evaluable Immunogenicity Population (EIP)

Time frame: Month 7. Geometric mean (95% Confidence Interval). Unit: Neutralization units per milliliter

Measure	2-Dose Clostridium Difficile Vaccine n = 795	3-Dose Clostridium Difficile Vaccine n = 812
Toxin A	693.0 (646.5 to 742.9)	845.7 (789.5 to 906.0)
Toxin B	4166.2 (3759.7 to 4616.7)	7342.9 (6633.1 to 8128.5)

2-Dose Clostridium Difficile Vaccine vs 3-Dose Clostridium Difficile Vaccine: Adjusted Geometric Mean Ratio: 0.82 (95% CI 0.74 to 0.90)
2-Dose Clostridium Difficile Vaccine vs 3-Dose Clostridium Difficile Vaccine: Adjusted Geometric Mean Ratio: 0.57 (95% CI 0.49 to 0.66)

Population analysed: EI7 population. All participants reported under 'Number of Participants Analyzed' contributed data to the table; however, may not have evaluable data for every row. "Number Analyzed" signifies participants with valid and determinate assay results for the specified assay at both baseline and the given sampling time point.

Primary outcome: Percentage of Participants Achieving Seroresponse for Clostridium Difficile Toxin A and Toxin B at Month 7 for EIP

Time frame: Month 7. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	2-Dose Clostridium Difficile Vaccine n = 795	3-Dose Clostridium Difficile Vaccine n = 812
Toxin A	32.2 (28.9 to 35.5)	33.9 (30.6 to 37.3)
Toxin B	56.7 (53.1 to 60.2)	73.5 (70.3 to 76.5)

2-Dose Clostridium Difficile Vaccine vs 3-Dose Clostridium Difficile Vaccine: Percentage difference: -1.8 (95% CI -6.4 to 2.9)
2-Dose Clostridium Difficile Vaccine vs 3-Dose Clostridium Difficile Vaccine: Percentage difference: -16.8 (95% CI -21.3 to -12.2)

Primary outcome: Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 1

Time frame: Up to 7 days after Dose 1 of investigational product at Month 0. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	2-Dose Clostridium Difficile Vaccine n = 983	3-Dose Clostridium Difficile Vaccine n = 988
Pain at injection site: Mild	19.1 (16.7 to 21.7)	17.5 (15.2 to 20.0)
Pain at injection site: Moderate	1.2 (0.6 to 2.1)	2.6 (1.7 to 3.8)
Pain at injection site: Severe	0.0 (0.0 to 0.4)	0.1 (0.0 to 0.6)
Pain at injection site: Potentially life threatening	0.0 (0.0 to 0.4)	0.0 (0.0 to 0.4)
Redness: Mild	0.9 (0.4 to 1.7)	0.6 (0.2 to 1.3)
Redness: Moderate	0.2 (0.0 to 0.7)	0.6 (0.2 to 1.3)
Redness: Severe	0.0 (0.0 to 0.4)	0.0 (0.0 to 0.4)
Redness: Potentially life threatening	0.0 (0.0 to 0.4)	0.0 (0.0 to 0.4)

Population analysed: Safety analysis set included all participants who received at least 1 dose of the investigational product. Here, "Overall Number of Participants Analyzed" signifies participants evaluable for this outcome measure.

Primary outcome: Percentage of Participants With Local Reactions by Maximum Severity Through 7 Days After Dose 2

Time frame: Up to 7 days after Dose 2 of investigational product at Month 1. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	2-Dose Clostridium Difficile Vaccine n = 937	3-Dose Clostridium Difficile Vaccine n = 940
Pain at injection site: Mild	5.4 (4.1 to 7.1)	24.0 (21.3 to 26.9)
Pain at injection site: Moderate	0.4 (0.1 to 1.1)	4.0 (2.9 to 5.5)
Pain at injection site: Severe	0.2 (0.0 to 0.8)	0.4 (0.1 to 1.1)
Pain at injection site: Potentially life threatening	0.0 (0.0 to 0.4)	0.0 (0.0 to 0.4)
Redness: Mild	0.0 (0.0 to 0.4)	2.3 (1.5 to 3.5)
Redness: Moderate	0.2 (0.0 to 0.8)	1.6 (0.9 to 2.6)
Redness: Severe	0.0 (0.0 to 0.4)	0.5 (0.2 to 1.2)
Redness: Potentially life threatening	0.0 (0.0 to 0.4)	0.0 (0.0 to 0.4)

2 secondary outcomes are reported in the full results.

Adverse events

Time frame: Local reactions and systemic events: within 7 days after vaccination (systematic assessment), other AEs: from Day 1 up to 1 month after last dose of vaccination (up to Month 7), all-cause mortality and SAEs: from Day 1 up to 6 months after last dose of vaccination (up to Month 12). Other adverse events reported at 1% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
2-Dose Clostridium Difficile Vaccine	141 of 994 (14.2%)	721 of 994 (72.5%)	15 of 994
3-Dose Clostridium Difficile Vaccine	136 of 997 (13.6%)	751 of 997 (75.3%)	7 of 997

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 10 Jan 2024.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
To obtain contact information for a study center near you, click here.Link provided by the sponsor.
Individual participant dataSharing planned: Yes. 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.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Pfizer CT.gov Call Center study director

Pfizer

52 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing Clostridium difficile in people with Clostridium Difficile Associated Disease, run by Pfizer at 52 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 4 inclusion and 17 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 10 Jan 2024. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 52 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 10 Jan 2024). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Adjusted Geometric Mean Concentration (GMC) of Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibodies at Month 7 for Evaluable Immunogenicity Population (EIP) (time frame: Month 7). The study lists 10 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT03918629.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 10 Jan 2024.