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Clostridioides difficile vaccine for people 65 and older

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

Phase 3 Interventional Pfizer · NCT07282665

This trial tests whether a vaccine can prevent C. difficile infections in people age 65 and older.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment32000 (estimated)
Ages65 Years and up
SexAll
SponsorPfizer Industry-sponsored
Locations158 sites (Athens, Alabama and 157 other locations)
Trial IDNCT07282665 on ClinicalTrials.gov

What this trial studies

Adults 65 and older with recent or planned contact with healthcare or recent antibiotic use are assigned to receive either an investigational C. difficile vaccine or a saline placebo by injection into the upper arm. The trial is event-driven and will continue until a predefined number of C. difficile–related diarrhea (pCDI) events occur, so individual participation averages about 3.5 years. Safety, tolerability, and the occurrence of pCDI events are monitored through planned visits and ongoing surveillance. People with prior CDI, major immunosuppression, prior C. difficile vaccines/antibodies, certain serious medical conditions, or prior intestinal resections are excluded.

Who should consider this trial

Good fit: Ideal candidates are adults aged 65 or older with recent or planned healthcare contact or recent antibiotic exposure who meet the trial's health and medication eligibility criteria.

Not a fit: People with a history of C. difficile infection, prior C. difficile vaccination or antibody therapy, significant immunosuppression, chronic frequent diarrhea, prior bowel resection, or serious uncontrolled medical conditions are unlikely to qualify or benefit.

Why it matters

Potential benefit: If effective, the vaccine could reduce C. difficile infections and related diarrhea in older adults.

How similar studies have performed: Earlier-phase C. difficile vaccine trials showed immune responses and acceptable safety, but no vaccine is yet licensed and definitive phase 3 efficacy evidence is still emerging.

Eligibility criteria

Show full inclusion / exclusion criteria 
Who Can Join the Study (Inclusion Criteria):

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

Who Cannot Join the Study (Exclusion Criteria):

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

Where this trial is running

Athens, Alabama and 157 other locations

+108 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Clostridioides Difficile Associated Disease
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.