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Clostridium difficile Vaccine

Phase 3

Clostridium Difficile Associated Disease | Monoclonal antibody | Infectious Disease |Pfizer, Inc.|Last Updated: Jan 10, 2024

Success Probability

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials5
Total Enrollment3,896

FDA Designations

No designations recorded

Clinical trial landscape

Clostridium difficile Vaccine · 6 trials · 2 indications

Phase 3 3Phase 2 2Phase 1 1
NCT03918629Clostridium Difficile Vaccine 2-Dose Versus 3-Dose StudyClostridium Difficile Associated Disease
COMPLETED1,994 Analytics
NCT03579459Evaluation Of Clostridium Difficile Vaccine Lot Consistency In Healthy Adults 65 To 85 Years Of AgeClostridium Difficile Associated Disease
COMPLETED1,317 Analytics
NCT03090191Clostridium Difficile Vaccine Efficacy TrialClostridium Difficile Infection
COMPLETED17,535 Analytics
PHASE3COMPLETED
Clostridium Difficile Vaccine 2-Dose Versus 3-Dose Study
Clostridium Difficile Associated DiseaseUnlock trial analytics
PHASE3COMPLETED
Evaluation Of Clostridium Difficile Vaccine Lot Consistency In Healthy Adults 65 To 85 Years Of Age
Clostridium Difficile Associated DiseaseUnlock trial analytics
PHASE3COMPLETED
Clostridium Difficile Vaccine Efficacy Trial
Clostridium Difficile InfectionUnlock trial analytics

Study Endpoints

Primary Endpoints

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

Geometric Mean Concentrations (GMCs) of Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibodies at Month 7
At Month 7

GMC was calculated as the mean of the assay results after making the logarithm transformation and then back transformation to its original scale. Confidence intervals (CIs) were back transformations of CIs based on the Student t distribution for the mean logarithm of the concentrations. Clostridium difficile toxin A and toxin B were inactivated by a combination of genetic mutations to decrease toxin activity and chemical treatments were done prior to final purification and formulation of the drug substance.

Percentage of Participants Reporting Local Reactions by Maximum Severity Within 7 Days After Vaccination 1
Within 7 days after Vaccination 1 at Month 0

Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an electronic diary (e-diary). Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Redness and swelling were measured and recorded in measuring device units. One measuring device unit= 0.5 centimeter (cm) and graded as mild: 2.5 to 5.0 cm, moderate: greater than (\>) 5.0 to 10.0 cm, severe: \>10.0 cm, Grade 4 indicated necrosis or exfoliative dermatitis for redness and necrosis for swelling. The maximum severity was defined as highest grading of each local reaction within 7 days of vaccination. Events were classified as Grade 4 based on study investigator's judgement.

Percentage of Participants Reporting Local Reactions by Maximum Severity Within 7 Days After Vaccination 2
Within 7 days after Vaccination 2 at Month 1

Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an e-diary. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Redness and swelling were measured and recorded in measuring device units. One measuring device unit= 0.5 cm and graded as mild: 2.5 to 5.0 cm, moderate: \> 5.0 to 10.0 cm, severe: \>10.0 cm, Grade 4 indicated necrosis or exfoliative dermatitis for redness and necrosis for swelling. The maximum severity was defined as highest grading of each local reaction within 7 days of vaccination. Events were classified as Grade 4 based on study investigator's judgement.

Percentage of Participants Reporting Local Reactions by Maximum Severity Within 7 Days After Vaccination 3
Within 7 days after Vaccination 3 at Month 6

Local reactions included pain at injection site, redness and swelling. These were recorded by participants in an e-diary. Pain at injection site was graded as mild: did not interfere with daily activity, moderate: interfered with daily activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Redness and swelling were measured and recorded in measuring device units. One measuring device unit= 0.5 cm and graded as mild: 2.5 to 5.0 cm, moderate: \> 5.0 to 10.0 cm, severe: \>10.0 cm, Grade 4 indicated necrosis or exfoliative dermatitis for redness and necrosis for swelling. The maximum severity was defined as highest grading of each local reaction within 7 days of vaccination. Events were classified as Grade 4 based on study investigator's judgement.

Percentage of Participants Reporting Systemic Events by Maximum Severity Within 7 Days After Vaccination 1
Within 7 days after Vaccination 1 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 Celsius \[deg C\]), moderate: (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C), grade 4: \>40 deg C. Fatigue, headache, joint pain and muscle pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours, moderate: \>2 times in 24 hours, severe: required intravenous hydration, grade 4: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event within 7 days of vaccination. Events were classified as Grade 4 based on study investigator's judgement.

Percentage of Participants Reporting Systemic Events by Maximum Severity Within 7 Days After Vaccination 2
Within 7 days after Vaccination 2 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), grade 4: \>40 deg C. Fatigue, headache, joint pain and muscle pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours, moderate: \>2 times in 24 hours, severe: required intravenous hydration, grade 4: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event within 7 days of vaccination. Events were classified as Grade 4 based on study investigator's judgement.

Percentage of Participants Reporting Systemic Events by Maximum Severity Within 7 Days After Vaccination 3
Within 7 days after Vaccination 3 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), grade 4: \>40 deg C. Fatigue, headache, joint pain and muscle pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours, moderate: \>2 times in 24 hours, severe: required intravenous hydration, grade 4: emergency room visit or hospitalization for hypotensive shock. The maximum severity was defined as highest grading of each systemic event within 7 days of vaccination. Events were classified as Grade 4 based on study investigator's judgement.

Percentage of Participants With Adverse Events (AEs) Through 1 Month After Last Study Vaccination
From Day 1 to 1 month after last vaccination (Up to Month 7)

An AE was defined as any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. AEs included both serious and all non-serious adverse events (NSAEs). Only AEs and NSAEs collected by non-systematic assessment (i.e., excluding local reactions and systemic events) were reported in this outcome measure.

Percentage of Participants Reporting Serious Adverse Events (SAEs)
From Day 1 to 1 month after last vaccination (Up to Month 7)

An SAE was defined as any untoward medical occurrence at any dose that resulted in any of the following outcomes: death; life-threatening (immediate risk of death); required inpatient hospitalization or prolongation of existing hospitalization; persistent or significant disability/incapacity (substantial disruption of the ability to conduct normal life functions); congenital anomaly/birth defect; or that was considered as an important medical event.

Number of First Primary Episodes of Clostridium Difficile Infection (CDI) (Definition 1) Follow-up After Dose 3
From 14 days after Dose 3 to the end of the surveillance period (mean follow-up after dose 3 was 34.2 months)

CDI definition 1 for a primary episode of CDI (no previous CDI onset in the prior 8 weeks) was defined as either a) presence of diarrhea, defined as passage of 3 or more unformed stools (Bristol stool chart types 5-7) in 24 or fewer consecutive hours, and stool sample that was positive for the toxin B gene (by polymerase chain reaction \[PCR)\] and positive for toxin A and/or toxin B, as measured in the central laboratory; or b) Pseudomembranous colitis diagnosed at colonoscopy, at surgery, or histopathologically; and corresponding stool sample that was positive for the toxin B gene (via PCR) as measured in the central laboratory. End of surveillance period was defined as accumulation of at least 40 CDI cases.

Number of First Primary Episodes of Clostridium Difficile Infection (CDI) (Definition 1) Follow-up After Dose 2
From 14 days after Dose 2 to the end of the surveillance period (mean follow-up after dose 2 was 36 months)

CDI definition 1 for a primary episode of CDI (no previous CDI onset in the prior 8 weeks) was defined as either a) presence of diarrhea, defined as passage of 3 or more unformed stools (Bristol stool chart types 5-7) in 24 or fewer consecutive hours, and stool sample that was positive for the toxin B gene (by PCR) and positive for toxin A and/or toxin B, as measured in the central laboratory; or b) Pseudomembranous colitis diagnosed at colonoscopy, at surgery, or histopathologically; and corresponding stool sample that was positive for the toxin B gene (via PCR) as measured in the central laboratory. End of surveillance period was defined as accumulation of at least 40 CDI cases.

Percentage of Participants Reporting Local Reactions Within 7 Days After Dose 1
Within 7 days after Dose 1 at Month 0

Local reactions included redness, swelling and pain at injection site. These were recorded by participants in an electronic diary (e-diary). Redness and swelling were measured and recorded in measuring device units. One measuring device unit= 0.5 centimeter (cm) and graded as mild: 2.5 to 5.0 cm, moderate: greater than (\>) 5.0 to 10.0 cm, severe: \>10.0 cm. Grade 4 indicated necrosis or exfoliative dermatitis for redness and 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. Grade 4 indicated emergency room visit or hospitalization.

Percentage of Participants Reporting Local Reactions Within 7 Days After Dose 2
Within 7 days after Dose 2 at Month 1

Local reactions included redness, swelling and pain at injection site. These were recorded by participants in an e-diary. Redness and swelling were measured and recorded in measuring device units. One measuring device unit= 0.5 cm and graded as mild: 2.5 to 5.0 cm, moderate: \> 5.0 to 10.0 cm, severe: \>10.0 cm. Grade 4 indicated necrosis or exfoliative dermatitis for redness and 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. Grade 4 indicated emergency room visit or hospitalization.

Percentage of Participants Reporting Local Reactions Within 7 Days After Dose 3
Within 7 days after Dose 3 at Month 6

Local reactions included redness, swelling and pain at injection site. These were recorded by participants in an e-diary. Redness and swelling were measured and recorded in measuring device units. One measuring device unit= 0.5 cm and graded as mild: 2.5 to 5.0 cm, moderate: \> 5.0 to 10.0 cm, severe: \>10.0 cm. Grade 4 indicated necrosis or exfoliative dermatitis for redness and 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. Grade 4 indicated emergency room visit or hospitalization.

Percentage of Participants Reporting Systemic Events Within 7 Days After Dose 1
Within 7 days after Dose 1 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 Celsius \[deg C\]), moderate: (38.5 to 38.9 deg C), severe (39.0 to 40.0 deg C), potentially life threatening (\> 40.0 deg C). Fatigue, headache, joint pain and muscle pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours, moderate: \>2 times in 24 hours, severe: required intravenous hydration, grade 4: emergency room visit or hospitalization for hypotensive shock.

Percentage of Participants Reporting Systemic Events Within 7 Days After Dose 2
Within 7 days after Dose 2 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), potentially life threatening (\> 40.0 deg C). Fatigue, headache, joint pain and muscle pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours, moderate: \>2 times in 24 hours, severe: required intravenous hydration, grade 4: emergency room visit or hospitalization for hypotensive shock.

Percentage of Participants Reporting Systemic Events Within 7 Days After Dose 3
Within 7 days after Dose 3 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), potentially life threatening (\> 40.0 deg C). Fatigue, headache, joint pain and muscle pain were graded as mild: did not interfere with activity, moderate: some interference with activity, severe: prevented daily activity, grade 4: emergency room visit or hospitalization. Vomiting was graded as mild: 1 to 2 times in 24 hours, moderate: \>2 times in 24 hours, severe: required intravenous hydration, grade 4: emergency room visit or hospitalization for hypotensive shock.

Number of Participants Reporting Adverse Events (AEs)
From Day 1 of Dose 1 to 1 Month after Dose 3 (7 Months)

An AE was defined as any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. AEs included both serious and all non-serious adverse events. An SAE was defined as any untoward medical occurrence at any dose that resulted in any of the following outcomes: death; life-threatening (immediate risk of death); required inpatient hospitalization or prolongation of existing hospitalization; persistent or significant disability/incapacity (substantial disruption of the ability to conduct normal life functions); congenital anomaly/birth defect; or that was considered as an important medical event. AEs included both SAEs and all Non-SAEs (except local and systemic events).

Number of Participants Reporting Serious Adverse Events (SAEs)
From Day 1 of Dose 1 up to 6 months after Dose 3 (up to Month 12)

An SAE was defined as any untoward medical occurrence at any dose that resulted in any of the following outcomes: death; life-threatening (immediate risk of death); required inpatient hospitalization or prolongation of existing hospitalization; persistent or significant disability/incapacity (substantial disruption of the ability to conduct normal life functions); congenital anomaly/birth defect; or that was considered as an important medical event.

Day 1, 8 and 30 Regimen: Percentage of Participants Achieving Prespecified Antibody Titer Level for Toxin A at Day 37
Day 37 (7 days after Vaccination 3 of Day 1, 8 and 30 regimen)

Toxin A antibodies (threshold \>= 219 neutralization units/mL) were measured using neutralization assay.

Month 0, 1 and 6 Regimen: Percentage of Participants Achieving Prespecified Antibody Titer Level for Toxin A at Month 7
Month 7 (1 month after Vaccination 3 of Month 0, 1 and 6 regimen)

Toxin A antibodies (threshold \>= 219 neutralization units/mL) were measured using neutralization assay.

Day 1, 8 and 30 Regimen: Percentage of Participants Achieving Prespecified Antibody Titer Level for Toxin B at Day 37
Day 37 (7 days after Vaccination 3 of Day 1, 8 and 30 regimen)

Toxin B antibodies (threshold \>= 2586 neutralization units/mL) were measured using neutralization assay.

Month 0, 1 and 6 Regimen: Percentage of Participants Achieving Prespecified Antibody Titer Level for Toxin B at Month 7
Month 7 (1 month after Vaccination 3 of Month 0, 1 and 6 regimen)

Toxin B antibodies (threshold \>= 2586 neutralization units/mL) were measured using neutralization assay.

Day 1, 8 and 30 Regimen: Percentage of Participants Achieving Prespecified Antibody Titer Level for Both Toxin A and Toxin B at Day 37
Day 37 (7 days after Vaccination 3 of Day 1, 8 and 30 regimen)

Toxin A and B antibodies (threshold \>= 219 and 2586 neutralization units/mL) were measured using neutralization assay.

Month 0, 1 and 6 Regimen: Percentage of Participants Achieving Prespecified Antibody Titer Level for Both Toxin A and Toxin B at Month 7
Month 7 (1 month after Vaccination 3 of Month 0, 1 and 6 regimen)

Toxin A and B antibodies (threshold \>= 219 and 2586 neutralization units/mL) were measured using neutralization assay.

Day 1, 8 and 30 Regimen: Percentage of Participants With Local Reactions by Severity Within 7 Days After Vaccination 1
within 7 days After Vaccination 1

Local reactions included pain at injection site, swelling and redness collected by using an electronic diary (e-diary). Pain was graded as: mild (grade 1) (did not interfere with activity), moderate (grade 2)(interfered with activity), severe (grade 3) (prevented daily activity) and grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.5-5.0 centimeter \[cm\]), moderate (\>5.0 to 10.0 cm), severe (\>10.0 cm) and grade 4 (necrosis).

Month 0, 1 and 6 Regimen: Percentage of Participants With Local Reactions by Severity Within 14 Days After Vaccination 1
within 14 days After Vaccination 1

Local reactions included pain at injection site, swelling and redness collected by using an electronic diary (e-diary). Pain was graded as: mild (did not interfere with activity), moderate (interfered with activity), severe (prevented daily activity) and grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.5-5.0 cm), moderate (\>5.0 to 10.0 cm), severe (\>10.0 cm) and grade 4 (necrosis).

Day 1, 8 and 30 Regimen: Percentage of Participants With Local Reactions by Severity Within 14 Days After Vaccination 2
within 14 days After Vaccination 2

Local reactions included pain at injection site, swelling and redness collected by using an electronic diary (e-diary). Pain was graded as: mild (did not interfere with activity), moderate (interfered with activity), severe (prevented daily activity) and grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.5-5.0 cm), moderate (\>5.0 to 10.0 cm), severe (\>10.0 cm) and grade 4 (necrosis).

Month 0, 1 and 6 Regimen: Percentage of Participants With Local Reactions by Severity Within 14 Days After Vaccination 2
within 14 days after Vaccination 2

Local reactions included pain at injection site, swelling and redness collected by using an electronic diary (e-diary). Pain was graded as: mild (did not interfere with activity), moderate (interfered with activity), severe (prevented daily activity) and grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.5-5.0 cm), moderate (\>5.0 to 10.0 cm), severe (\>10.0 cm) and grade 4 (necrosis).

Day 1, 8 and 30 Regimen: Percentage of Participants With Local Reactions by Severity Within 14 Days After Vaccination 3
within 14 days after Vaccination 3

Local reactions included pain at injection site, swelling and redness collected by using an electronic diary (e-diary). Pain was graded as: mild (did not interfere with activity), moderate (interfered with activity), severe (prevented daily activity) and grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.5-5.0 cm), moderate (\>5.0 to 10.0 cm), severe (\>10.0 cm) and grade 4 (necrosis).

Month 0, 1 and 6 Regimen: Percentage of Participants With Local Reactions by Severity Within 14 Days After Vaccination 3
within 14 days after Vaccination 3

Local reactions included pain at injection site, swelling and redness collected by using an electronic diary (e-diary). Pain was graded as: mild (did not interfere with activity), moderate (interfered with activity), severe (prevented daily activity) and grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.5-5.0 cm), moderate (\>5.0 to 10.0 cm), severe (\>10.0 cm) and grade 4 (necrosis).

Day 1, 8 and 30 Regimen: Percentage of Participants With Systemic Events by Severity Within 7 Days After Vaccination 1
within 7 days after Vaccination 1

Systemic events included fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, new or worsening joint pain and were recorded by using an e-diary. Fever was graded as mild (38.0 to 38.4 degree Celsius (C)), moderate (38.5 to 38.9 degree C), severe (39.0 to 40.0 degree C), grade 4 (\>40.0 degree C). Vomiting was graded as mild (1-2 times in 24 hours), moderate (\>2 times in 24 hours), severe (required intravenous hydration) and grade 4 (hospitalization for hypotensive shock). Diarrhea was graded as mild (2-3 loose stools in 24 hours), moderate (4-5 loose stools in 24 hours), severe (\>=6 stools in 24 hours) and grade 4 (hospitalization). Headache, fatigue, new or worsening muscle pain and new or worsening joint pain was graded as mild (no interference with activity), moderate (some interference with activity), severe (prevents daily activity) and grade 4 (hospitalization).

Month 0, 1 and 6 Regimen: Percentage of Participants With Systemic Events by Severity Within 14 Days After Vaccination 1
within 14 days after Vaccination 1

Systemic events included fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, new or worsening joint pain and were recorded by using an e-diary. Fever was graded as mild (38.0 to 38.4 C), moderate (38.5 to 38.9 degree C), severe (39.0 to 40.0 degree C), grade 4 (\>40.0 degree C). Vomiting was graded as mild (1-2 times in 24 hours), moderate (\>2 times in 24 hours), severe (required intravenous hydration) and grade 4 (hospitalization for hypotensive shock). Diarrhea was graded as mild (2-3 loose stools in 24 hours), moderate (4-5 loose stools in 24 hours), severe (\>=6 stools in 24 hours) and grade 4 (hospitalization). Headache, fatigue, new or worsening muscle pain and new or worsening joint pain was graded as mild (no interference with activity), moderate (some interference with activity), severe (prevents daily activity) and grade 4 (hospitalization).

Day 1, 8 and 30 Regimen: Percentage of Participants With Systemic Events by Severity Within 14 Days After Vaccination 2
within 14 days after Vaccination 2

Systemic events included fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, new or worsening joint pain and were recorded by using an e-diary. Fever was graded as mild (38.0 to 38.4 C), moderate (38.5 to 38.9 degree C), severe (39.0 to 40.0 degree C), grade 4 (\>40.0 degree C). Vomiting was graded as mild (1-2 times in 24 hours), moderate (\>2 times in 24 hours), severe (required intravenous hydration) and grade 4 (hospitalization for hypotensive shock). Diarrhea was graded as mild (2-3 loose stools in 24 hours), moderate (4-5 loose stools in 24 hours), severe (\>=6 stools in 24 hours) and grade 4 (hospitalization). Headache, fatigue, new or worsening muscle pain and new or worsening joint pain was graded as mild (no interference with activity), moderate (some interference with activity), severe (prevents daily activity) and grade 4 (hospitalization).

Month 0, 1 and 6 Regimen: Percentage of Participants With Systemic Events by Severity Within 14 Days After Vaccination 2
within 14 days after Vaccination 2

Systemic events included fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, new or worsening joint pain and were recorded by using an e-diary. Fever was graded as mild (38.0 to 38.4 C), moderate (38.5 to 38.9 degree C), severe (39.0 to 40.0 degree C), grade 4 (\>40.0 degree C). Vomiting was graded as mild (1-2 times in 24 hours), moderate (\>2 times in 24 hours), severe (required intravenous hydration) and grade 4 (hospitalization for hypotensive shock). Diarrhea was graded as mild (2-3 loose stools in 24 hours), moderate (4-5 loose stools in 24 hours), severe (\>=6 stools in 24 hours) and grade 4 (hospitalization). Headache, fatigue, new or worsening muscle pain and new or worsening joint pain was graded as mild (no interference with activity), moderate (some interference with activity), severe (prevents daily activity) and grade 4 (hospitalization).

Day 1, 8 and 30 Regimen: Percentage of Participants With Systemic Events by Severity Within 14 Days After Vaccination 3
within 14 days after Vaccination 3

Systemic events included fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, new or worsening joint pain and were recorded by using an e-diary. Fever was graded as mild (38.0 to 38.4 C), moderate (38.5 to 38.9 degree C), severe (39.0 to 40.0 degree C), grade 4 (\>40.0 degree C). Vomiting was graded as mild (1-2 times in 24 hours), moderate (\>2 times in 24 hours), severe (required intravenous hydration) and grade 4 (hospitalization for hypotensive shock). Diarrhea was graded as mild (2-3 loose stools in 24 hours), moderate (4-5 loose stools in 24 hours), severe (\>=6 stools in 24 hours) and grade 4 (hospitalization). Headache, fatigue, new or worsening muscle pain and new or worsening joint pain was graded as mild (no interference with activity), moderate (some interference with activity), severe (prevents daily activity) and grade 4 (hospitalization).

Month 0, 1 and 6 Regimen: Percentage of Participants With Systemic Events by Severity Within 14 Days After Vaccination 3
within 14 days after Vaccination 3

Systemic events included fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, new or worsening joint pain and were recorded by using an e-diary. Fever was graded as mild (38.0 to 38.4 C), moderate (38.5 to 38.9 degree C), severe (39.0 to 40.0 degree C), grade 4 (\>40.0 degree C). Vomiting was graded as mild (1-2 times in 24 hours), moderate (\>2 times in 24 hours), severe (required intravenous hydration) and grade 4 (hospitalization for hypotensive shock). Diarrhea was graded as mild (2-3 loose stools in 24 hours), moderate (4-5 loose stools in 24 hours), severe (\>=6 stools in 24 hours) and grade 4 (hospitalization). Headache, fatigue, new or worsening muscle pain and new or worsening joint pain was graded as mild (no interference with activity), moderate (some interference with activity), severe (prevents daily activity) and grade 4 (hospitalization).

Day 1, 8 and 30 Regimen: Percentage of Participants With Treatment Emergent Adverse Events (AEs)
From Vaccination 1 up to 28 days after Vaccination 3 (Day 58)

An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Treatment-emergent are events between first dose of study drug and up to 28 days after last dose of study drug that were absent before treatment or that worsened relative to pretreatment state.

Month 0, 1 and 6 Regimen: Percentage of Participants With Treatment Emergent Adverse Events (AEs)
From Vaccination 1 up to 28 days after Vaccination 3 (Day 208)

An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Treatment-emergent are events between first dose of study drug and up to 28 days after last dose of study drug that were absent before treatment or that worsened relative to pretreatment state.

Day 1, 8 and 30 Regimen: Percentage of Participants With Treatment Emergent Serious Adverse Events (SAEs)
From Vaccination 1 up to 6 months after Vaccination 3 (Month 7)

An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. SAE was an AE resulting 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; lack of efficacy in an approved indication. Treatment-emergent serious adverse events are events between first dose of study drug and up to 6 months after last dose of study drug that were absent before treatment or that worsened relative to pretreatment state.

Month 0, 1 and 6 Regimen: Percentage of Participants With Treatment Emergent Serious Adverse Events (SAEs)
From Vaccination 1 up to 6 months after Vaccination 3 (Month 12)

An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. SAE was an AE resulting 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; lack of efficacy in an approved indication. Treatment-emergent serious adverse events are events between first dose of study drug and up to 6 months after last dose of study drug that were absent before treatment or that worsened relative to pretreatment state.

Percentage of Participants Reporting Prespecified Local Reactions Within 7 Days After Dose 1 (50- to 64-Year Age Cohort)
From Day of Dose 1 vaccination to within 7 days after Dose 1

Pain at injection site: mild=does not interfere with activity; moderate=interferes with activity; severe=prevents daily activity; Grade 4=emergency department visit or hospitalization. Redness/swelling: Mild=2.5 to 5.0 cm; moderate= \>5.0 to 10.0 cm; severe= \>10 cm; Grade 4=necrosis or exfoliative dermatitis for redness category and only necrosis for swelling category. Any local reaction=any pain at the injection site, any swelling, or any redness.

Percentage of Participants Reporting Prespecified Local Reactions Within 14 Days After Dose 2 (50- to 64-Year Age Cohort)
From Day of Dose 2 vaccination to within 14 days after Dose 2

Pain at injection site: mild=does not interfere with activity; moderate=interferes with activity; severe=prevents daily activity; Grade 4=emergency department visit or hospitalization. Redness/swelling: Mild=2.5 to 5.0 cm; moderate= \>5.0 to 10.0 cm; severe= \>10 cm; Grade 4=necrosis or exfoliative dermatitis for redness category and only necrosis for swelling category. Any local reaction=any pain at the injection site, any swelling, or any redness.

Percentage of Participants Reporting Prespecified Local Reactions Within 14 Days After Dose 3 (50- to 64-Year Age Cohort)
From Day of Dose 3 vaccination to within 14 days after Dose 3

Pain at injection site: mild=does not interfere with activity; moderate=interferes with activity; severe=prevents daily activity; Grade 4=emergency department visit or hospitalization. Redness/swelling: Mild=2.5 to 5.0 cm; moderate= \>5.0 to 10.0 cm; severe= \>10 cm; Grade 4=necrosis or exfoliative dermatitis for redness category and only necrosis for swelling category. Any local reaction=any pain at the injection site, any swelling, or any redness.

Percentage of Participants Reporting Systemic Events Within 7 Days After Dose 1 (50- to 64-Year Age Cohort)
From Day of Dose 1 vaccination to within 7 days of Dose 1

Fever=temperature ≥38.0°C (100.4°C): Mild=38.0°C to 38.4°C (100.4°F-101.1°F); moderate=38.5°C to 38.9°C (101.2°F-102.0°F); severe=39.0°C to 40.0°C (102.1°F-104.0°F); Grade 4= \>40.0°C (\>104.0°F). Vomiting: Mild=1 to 2 times in 24 hours; moderate= \>2 times in 24 hours; severe=requires intravenous hydration; Grade 4=emergency department visit or hospitalization for hypotensive shock. Diarrhea: Mild=2 to 3 loose stools in 24 hours; moderate=4 to 5 loose stools in 24 hours; severe= ≥6 loose stools in 24 hours; Grade 4=emergency department visit or hospitalization. Headache, fatigue, new or worsening joint or muscle pain: Mild=no interference with activity; moderate=some interference with activity; severe=significant interference with activity, prevents daily activity; Grade 4=emergency department visit or hospitalization. Any systemic event: Fever ≥38.0°C, vomiting, diarrhea, headache, fatigue, or new or worsening muscle or joint pain.

Percentage of Participants With A Systemic Event Within 14 Days of Dose 2 (50- to 64-Year Age Cohort)
From Day of Dose 2 vaccination to within 14 days after Dose 2

Fever=temperature ≥38.0°C (100.4°C): Mild=38.0°C to 38.4°C (100.4°F-101.1°F); moderate=38.5°C to 38.9°C (101.2°F-102.0°F); severe=39.0°C to 40.0°C (102.1°F-104.0°F); Grade 4= \>40.0°C (\>104.0°F). Vomiting: Mild=1 to 2 times in 24 hours; moderate= \>2 times in 24 hours; severe=requires intravenous hydration; Grade 4=emergency department visit or hospitalization for hypotensive shock. Diarrhea: Mild=2 to 3 loose stools in 24 hours; moderate=4 to 5 loose stools in 24 hours; severe= ≥6 loose stools in 24 hours; Grade 4=emergency department visit or hospitalization. Headache, fatigue, new or worsening joint or muscle pain: Mild=no interference with activity; moderate=some interference with activity; severe=significant interference with activity, prevents daily activity; Grade 4=emergency department visit or hospitalization. Any systemic event: Fever ≥38.0°C, vomiting, diarrhea, headache, fatigue, or new or worsening muscle or joint pain.

Percentage of Participants Reporting Systemic Events Within 14 Days After Dose 3 (50- to 64-Year Age Cohort)
From Day of Dose 3 vaccination to within 14 days after Dose 3

Fever=temperature ≥38.0°C (100.4°C): Mild=38.0°C to 38.4°C (100.4°F-101.1°F); moderate=38.5°C to 38.9°C (101.2°F-102.0°F); severe=39.0°C to 40.0°C (102.1°F-104.0°F); Grade 4= \>40.0°C (\>104.0°F). Vomiting: Mild=1 to 2 times in 24 hours; moderate= \>2 times in 24 hours; severe=requires intravenous hydration; Grade 4=emergency department visit or hospitalization for hypotensive shock. Diarrhea: Mild=2 to 3 loose stools in 24 hours; moderate=4 to 5 loose stools in 24 hours; severe= ≥6 loose stools in 24 hours; Grade 4=emergency department visit or hospitalization. Headache, fatigue, new or worsening joint or muscle pain: Mild=no interference with activity; moderate=some interference with activity; severe=significant interference with activity, prevents daily activity; Grade 4=emergency department visit or hospitalization. Any systemic event: Fever ≥38.0°C, vomiting, diarrhea, headache, fatigue, or new or worsening muscle or joint pain.

Percentage of Participants Reporting Adverse Events (AEs) to Month 2 and Serious AEs (SAEs) to Month 13 (50- to 64-Year Age Cohort)
AEs: From informed consent to Visit 6 (Month 2). SAEs: From informed consent to Visit 9 (Month 13)

An AE is any untoward medical occurrence in a clinical investigation participant administered a product or medical device; the event need not necessarily have a causal relationship with the treatment or usage. An SAE is any untoward medical occurrence at any dose that results in death, persistent or significant disability/incapacity, or congenital anomaly/birth defect; is life-threatening; or requires or prolongs inpatient hospitalization.

Percentage of Participants With A Local Reaction Within 7 Days of Dose 1 (65- to 85-Year Age Cohort)
From Day of Dose 1 vaccination to within 7 days of Dose 1

Pain at injection site: mild=does not interfere with activity; moderate=interferes with activity; severe=prevents daily activity; Grade 4=emergency department visit or hospitalization. Redness/swelling: Mild=2.5 to 5.0 cm; moderate= \>5.0 to 10.0 cm; severe= \>10 cm; Grade 4=necrosis or exfoliative dermatitis for redness category and only necrosis for swelling category. Any local reaction=any pain at the injection site, any swelling, or any redness.

Percentage of Participants With A Local Reaction Within 14 Days After Dose 2 (65- to 85-Year Age Cohort)
From Day of Dose 2 vaccination to 14 days after Dose 2

Pain at injection site: mild=does not interfere with activity; moderate=interferes with activity; severe=prevents daily activity; Grade 4=emergency department visit or hospitalization. Redness/swelling: Mild=2.5 to 5.0 cm; moderate= \>5.0 to 10.0 cm; severe= \>10 cm; Grade 4=necrosis or exfoliative dermatitis for redness category and only necrosis for swelling category. Any local reaction=any pain at the injection site, any swelling, or any redness.

Percentage of Participants With A Local Reaction Within 14 Days After Dose 3 (65- to 85-Year Age Cohort)
From Day of Dose 3 vaccination to 14 days after Dose 3

Pain at injection site: mild=does not interfere with activity; moderate=interferes with activity; severe=prevents daily activity; Grade 4=emergency department visit or hospitalization. Redness/swelling: Mild=2.5 to 5.0 cm; moderate= \>5.0 to 10.0 cm; severe= \>10 cm; Grade 4=necrosis or exfoliative dermatitis for redness category and only necrosis for swelling category. Any local reaction=any pain at the injection site, any swelling, or any redness.

Percentage of Participants With A Systemic Event Within 7 Days of Dose 1 (65- to 85-Year Age Cohort)
From Day of Dose 1 vaccination to within 7 days of Dose 1

Fever=temperature ≥38.0°C (100.4°C): Mild=38.0°C to 38.4°C (100.4°F-101.1°F); moderate=38.5°C to 38.9°C (101.2°F-102.0°F); severe=39.0°C to 40.0°C (102.1°F-104.0°F); Grade 4= \>40.0°C (\>104.0°F). Vomiting: Mild=1 to 2 times in 24 hours; moderate= \>2 times in 24 hours; severe=requires intravenous hydration; Grade 4=emergency department visit or hospitalization for hypotensive shock. Diarrhea: Mild=2 to 3 loose stools in 24 hours; moderate=4 to 5 loose stools in 24 hours; severe= ≥6 loose stools in 24 hours; Grade 4=emergency department visit or hospitalization. Headache, fatigue, new or worsening joint or muscle pain: Mild=no interference with activity; moderate=some interference with activity; severe=significant interference with activity, prevents daily activity; Grade 4=emergency department visit or hospitalization. Any systemic event: Fever ≥38.0°C, vomiting, diarrhea, headache, fatigue, or new or worsening muscle or joint pain.

Percentage of Participants With a Systemic Event Within 14 Days of Dose 2 (65- to 85-Year Age Cohort)
From Day of Dose 2 vaccination to within 14 days after Dose 2

Fever=temperature ≥38.0°C (100.4°C): Mild=38.0°C to 38.4°C (100.4°F-101.1°F); moderate=38.5°C to 38.9°C (101.2°F-102.0°F); severe=39.0°C to 40.0°C (102.1°F-104.0°F); Grade 4= \>40.0°C (\>104.0°F). Vomiting: Mild=1 to 2 times in 24 hours; moderate= \>2 times in 24 hours; severe=requires intravenous hydration; Grade 4=emergency department visit or hospitalization for hypotensive shock. Diarrhea: Mild=2 to 3 loose stools in 24 hours; moderate=4 to 5 loose stools in 24 hours; severe= ≥6 loose stools in 24 hours; Grade 4=emergency department visit or hospitalization. Headache, fatigue, new or worsening joint or muscle pain: Mild=no interference with activity; moderate=some interference with activity; severe=significant interference with activity, prevents daily activity; Grade 4=emergency department visit or hospitalization. Any systemic event: Fever ≥38.0°C, vomiting, diarrhea, headache, fatigue, or new or worsening muscle or joint pain.

Percentage of Participants Reporting Systemic Events Within 14 Days After Dose 3 (65- to 85-Year Age Cohort)
From Day of Dose 3 vaccination to within 14 days after Dose 3

Fever=temperature ≥38.0°C (100.4°C): Mild=38.0°C to 38.4°C (100.4°F-101.1°F); moderate=38.5°C to 38.9°C (101.2°F-102.0°F); severe=39.0°C to 40.0°C (102.1°F-104.0°F); Grade 4= \>40.0°C (\>104.0°F). Vomiting: Mild=1 to 2 times in 24 hours; moderate= \>2 times in 24 hours; severe=requires intravenous hydration; Grade 4=emergency department visit or hospitalization for hypotensive shock. Diarrhea: Mild=2 to 3 loose stools in 24 hours; moderate=4 to 5 loose stools in 24 hours; severe= ≥6 loose stools in 24 hours; Grade 4=emergency department visit or hospitalization. Headache, fatigue, new or worsening joint or muscle pain: Mild=no interference with activity; moderate=some interference with activity; severe=significant interference with activity, prevents daily activity; Grade 4=emergency department visit or hospitalization. Any systemic event: Fever ≥38.0°C, vomiting, diarrhea, headache, fatigue, or new or worsening muscle or joint pain.

Percentage of Participants Reporting Adverse Events (AEs) to Month 2 and Serious AEs (SAEs) to Month 13 (65- to 85-Year Age Cohort)
AEs: From informed consent to Visit 6 (Month 2). SAEs: From informed consent to Visit 9 (Month 13)

An AE is any untoward medical occurrence in a clinical investigation participant administered a product or medical device; the event need not necessarily have a causal relationship with the treatment or usage. An SAE is any untoward medical occurrence at any dose that results in death, persistent or significant disability/incapacity, or congenital anomaly/birth defect; is life-threatening; or requires or prolongs inpatient hospitalization.

Proportions of subjects reporting local reactions (pain, erythema, and induration) and their severity, as self-reported on e-diaries
Up to 14 days after each vaccination
Proportions of subjects reporting systemic events (fever, vomiting, diarrhea, headache, fatigue, new or worsening muscle pain, and new or worsening joint pain) and their severity, as self-reported on e-diaries
Up to 14 days after each vaccination
Proportions of subjects reporting AEs (categorized according to the Medical Dictionary for Regulatory Activities [MedDRA])
From the first vaccination up to 28 days after the last vaccination
Proportions of subjects reporting SAEs (categorized according to the Medical Dictionary for Regulatory Activities [MedDRA])
From the first vaccination until 6 months after the last vaccination
Proportions of subjects with abnormal hematology and blood chemistry laboratory assessments
7 days or 14 days after each vaccination

Secondary Endpoints

Adjusted Geometric Mean Concentration for Clostridium Difficile Toxin A and Toxin B Specific Neutralizing Antibody at Month 12 for EIP
Month 12
Percentage of Participants Achieving Seroresponse for Clostridium Difficile Toxin A and Toxin B at Month 12 for EIP
Month 12
Number of All Episodes of CDI (Definition 1 and 2) After Dose 3
From 14 days after Dose 3 to the end of the surveillance period (mean follow-up after dose 3 was 34.2 months)
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposePREVENTION

Treatment Arms

ArmTypeDescription
Clostridium difficile vaccine - 3 doseEXPERIMENTALAll 3 doses are the Clostridium difficile vaccine
Clostridium difficile vaccine - 2 doseEXPERIMENTAL2 of the 3 doses are the Clostridium difficile vaccine with the other being placebo
Clostridium difficile vaccine Lot 1ACTIVE_COMPARATOR -
Clostridium difficile vaccine Lot 2ACTIVE_COMPARATOR -
Clostridium difficile vaccine Lot 3ACTIVE_COMPARATOR -
PlaceboPLACEBO_COMPARATORNormal saline solution (0.9% sodium chloride)
Clostridium difficile vaccineEXPERIMENTAL -
Low-dose C. difficile Vaccine (accelerated schedule)EXPERIMENTAL -
High-dose C. difficile Vaccine (accelerated schedule)EXPERIMENTAL -
Placebo (accelerated schedule)PLACEBO_COMPARATOR -
Low-dose C. difficile Vaccine (non-accelerated schedule)EXPERIMENTAL -
High-Dose C. difficile Vaccine (non-accelerated schedule)EXPERIMENTAL -
Placebo (non-accelerated schedule)PLACEBO_COMPARATOR -
High dose of C. difficile vaccineEXPERIMENTAL -
Low dose of C. difficile vaccineEXPERIMENTAL -

Interventions

NameTypeDescription
Clostridium difficileBIOLOGICALToxoid-based Clostridium difficile vaccine
PlaceboBIOLOGICALNormal saline solution (0.9% sodium chloride)
Clostridium difficile vaccineBIOLOGICALToxoid based Clostridium difficile vaccine
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Eligibility Criteria

Age Range50 Years to N/A
SexALL
Healthy VolunteersYes
Study Sites52

Inclusion Criteria: * 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. * A...

Countries:United StatesArgentinaAustraliaBelgiumBulgariaCanadaChileColombiaCzechiaFinlandFranceGermanyHungaryJapanPeruPolandPortugalSlovakiaSouth KoreaSpainSwedenTaiwanUnited Kingdom
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Frequently asked questions about Clostridium difficile Vaccine

What is Clostridium difficile Vaccine used for?

Clostridium difficile Vaccine is an investigational vaccine being developed to prevent Clostridium difficile infection and Clostridium difficile associated disease. It is designed for use in adults, with clinical trials enrolling healthy adults aged 50 years and older, including those up to 85 years of age.

Who makes Clostridium difficile Vaccine?

Clostridium difficile Vaccine is being developed by Pfizer, Inc., a biopharmaceutical company traded on the New York Stock Exchange under the ticker symbol PFE. Pfizer is conducting clinical trials to evaluate the vaccine's safety, tolerability, and immunogenicity in adult populations.

What phase is Clostridium difficile Vaccine in?

Clostridium difficile Vaccine is in Phase 3 clinical development. It has completed Phase 1, Phase 2, and Phase 3 trials, with a total of five completed studies involving 17,535 participants. The vaccine remains investigational and has not been approved by regulatory authorities.

What clinical trials is Clostridium difficile Vaccine in?

Clostridium difficile Vaccine has completed five clinical trials, including NCT02117570, NCT02561195, NCT02725437, and NCT03918629. These studies evaluated different dosing schedules, including 2-dose and 3-dose regimens, in healthy adults aged 50 to 85 years across the United States and Japan.

Is Clostridium difficile Vaccine a monoclonal antibody?

Clostridium difficile Vaccine is classified as a monoclonal antibody modality, though it functions as a vaccine to prevent Clostridium difficile infection. It is being studied in randomized, double-blind, placebo-controlled trials to assess its efficacy in preventing Clostridium difficile associated disease.