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Clostridium Difficile Vaccine 2-Dose Versus 3-Dose Study

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details. Identifier: NCT03918629
Recruitment Status : Recruiting
First Posted : April 17, 2019
Last Update Posted : July 23, 2019
Information provided by (Responsible Party):

Brief Summary:
This study will investigate a Clostridium difficile vaccine in healthy adults 50 years of age and older. In half the healthy adults, all 3 doses given are the Clostridium difficile vaccine, and in half the healthy 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.

Condition or disease Intervention/treatment Phase
Clostridium Difficile Associated Disease Biological: Clostridium difficile Biological: Placebo Phase 3

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Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 1960 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Prevention
Actual Study Start Date : April 1, 2019
Estimated Primary Completion Date : June 9, 2020
Estimated Study Completion Date : December 17, 2020

Arm Intervention/treatment
Experimental: Clostridium difficile vaccine - 3 dose
All 3 doses are the Clostridium difficile vaccine
Biological: Clostridium difficile
Toxoid-based Clostridium difficile vaccine

Experimental: Clostridium difficile vaccine - 2 dose
2 of the 3 doses are the Clostridium difficile vaccine with the other being placebo
Biological: Clostridium difficile
Toxoid-based Clostridium difficile vaccine

Biological: Placebo
Normal saline solution (0.9% sodium chloride)

Primary Outcome Measures :
  1. C difficile toxin A- and toxin B-specific neutralizing antibody levels at Month 7 in each regimen [ Time Frame: At Month 7 ]
    As measured by the central laboratory

  2. Percentage of subjects reporting local reactions [ Time Frame: Up to 7 days following each vaccination ]
    Pain, erythema, and induration, as self-reported in electronic diaries

  3. Percentage of subjects reporting systemic events [ Time Frame: Up to 7 days following each vaccination ]
    Fever, vomiting, headache, fatigue, new or worsening muscle pain, and new or worsening joint pain, as self-reported in electronic diaries

  4. Percentage of subjects reporting nonserious adverse events [ Time Frame: Up to 1 month after the last dose of vaccine ]
    As elicited by investigational site staff

  5. Percentage of subjects reporting serious adverse evets [ Time Frame: Up to 6 months after the last dose of vaccine ]
    As elicited by investigational site staff

Secondary Outcome Measures :
  1. Toxin A- and toxin B-specific neutralizing antibody levels, expressed as geometric mean concentrations in each regimen [ Time Frame: At Month 12 ]
    As measured by the central laboratory

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

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Ages Eligible for Study:   50 Years and older   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

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.
  • Ability to be contacted by telephone during study participation.

Exclusion Criteria:

  • 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.
    • 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.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT03918629

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Contact: Pfizer Call Center 1-800-718-1021

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Sponsors and Collaborators
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Study Director: Pfizer Call Center Pfizer

Additional Information:
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Responsible Party: Pfizer Identifier: NCT03918629    
Other Study ID Numbers: B5091019
First Posted: April 17, 2019    Key Record Dates
Last Update Posted: July 23, 2019
Last Verified: July 2019
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Yes
Plan Description: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at:

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Studies a U.S. FDA-regulated Drug Product: Yes
Studies a U.S. FDA-regulated Device Product: No
Keywords provided by Pfizer:
Clostridium Difficile
Additional relevant MeSH terms:
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Clostridium Infections
Gram-Positive Bacterial Infections
Bacterial Infections
Immunologic Factors
Physiological Effects of Drugs