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

Phase 3RecruitingNCT07282665

Pfizer32,000 enrolled

Overview

The purpose of the study is to learn about how effective, safe, and tolerable the Clostridioides difficile (C. difficile) vaccine is in decreasing the number of C. difficile infections (pCDI) in adults 65 years of age or older. The participants will receive either the C. difficile vaccine or placebo (saline). A placebo does not contain any active ingredients. The vaccines will be given as a shot into the upper arm muscle. This study looks at the number of diarrhea (loose stools) events related to a C. difficile infection, so the length of the study can change. If these events happen quickly, the study may finish sooner; if they happen slowly, it could take longer. Sometimes, the study might stop early if the vaccine clearly works or clearly doesn't. Participants will stay in the study until enough events have occurred to answer the main question. On average, each person is expected to take part for up to about three and a half years. During this time, participants will have 3 planned clinical visits and 3 planned phone visits. After these visits, more scheduled clinic visits will happen every year until the end of study. Besides the scheduled study visits, if at any time during the study a participant has 3 or more loose stools in 24 hours, they will be asked to save the next one (the fourth or later) and contact the study site. The study site will check to see if it could be a C. difficile infection. This check may happen at the clinic or through a phone or video call.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

TRIPLE

Enrollment

32,000

Conditions

Clostridioides Difficile Associated Disease

Eligibility

Sex: ALLMin age: 65 YearsHealthy volunteers:

Medical Language ↔ Plain English

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.

Outcomes

Primary Outcomes

The percentage of participants reporting local reactions

Injection site pain, redness, and swelling as self-reported in electronic diaries

Time frame: For 7 days after each vaccination

The percentage of participants reporting systemic events

Fever, vomiting, fatigue, headache, muscle pain, and joint pain as self-reported in electronic diaries

Time frame: For 7 days after each vaccination

Percentage of participants reporting adverse events

As elicited by investigator site staff

Time frame: From each vaccination through 1 month after each vaccination

Percentage of participants reporting serious adverse events

As elicited by investigator site staff

Time frame: From Vaccination 1 (Day 1) through 12 months after Vaccination 2 (last dose) (18 months)

The incidence of the first episode of medically attended and clinically meaningful primary Clostridioides difficile infection (CDI)

First episode of medically attended and clinically meaningful primary CDI incidence per 1000 person- years of follow- up