To Understand the Safety and Effects of a C. Difficile Vaccine With New Adds-Ons That Will Be Given to Healthy Adults

Summary

An antibody is a substance your body makes to fight off infection. This study will explore the safety and antibody response of a vaccine to prevent severe diarrhea caused by a germ called Clostridoides difficile (C. diff). Three new formulations of the C. diff vaccine will be used in this study, in addition to a C. diff vaccine formulation that has been studied in previous clinical trials.

The purpose of this study is to understand if giving the new C. diff vaccine formulations helps people make as many antibodies as giving the previously studied C. diff vaccine formulation.

The study is divided into 2 phases.

Phase 1 will evaluate 3 new formulations of the C. diff vaccine and 2 dosing schedules spread out over 2 months or 6 months.

The Phase 1 portion of the study is seeking participants:

* who are healthy adults of 65 to 84 years of age
* who have not had a C. diff infection before
* who have not received a C. diff vaccine or C. diff monoclonal antibody therapy before.

All participants in Phase 1 will receive study injections with active vaccine or placebo at each vaccination visit, depending on the vaccine group to which they are assigned. A placebo does not contain any active ingredients. Participants in Phase 1 will attend at least 9 study visits and will take part in the study for approximately 18 months. Based on the results of Phase 1, 1 or 2 of the new C. diff vaccine formulations will be chosen for further study in Phase 2.

Phase 2 will evaluate the safety and effects of the new C. diff vaccine formulation(s) chosen in Phase 1.

The Phase 2 portion of the study is seeking participants:

* who are healthy adults ≥65 years of age; and 50 through 64 years of age (Cohort 4 only)
* who have not had a C. diff infection before
* who have not received a C. diff vaccine or C. diff monoclonal antibody therapy before.

Phase 2 participants will receive active C. diff vaccine or placebo at each vaccination visit. Participants in Phase 2 will attend at least 6 and up to 12 study visits and will take part in the study for up to 4 years.

A booster stage for selected participants in Phase 2 will have participants receive active C. diff vaccine or placebo to examine immune persistence. The booster stage participants will attend at least 10 additional study visits and will take part in the study for 6 years.

A newly added cohort will evaluate the safety and effects of active C. diff vaccine formulation in participants 50 through 64 years of age. Participants will receive C. diff vaccine or placebo and will attend at least 6 study visits over a period of 18 months.

Conditions

• Clostridoides Difficile Associated Disease

Interventions

BIOLOGICAL

C. difficile vaccine (previously studied formulation).

Toxoid based Clostridioides difficile vaccine (previously studied formulation) given as an intramuscular injection

BIOLOGICAL

C. difficile vaccine formulation 1.

C. difficile vaccine formulation 1 given as an intramuscular injection

BIOLOGICAL

C. difficile vaccine formulation 2.

C. difficile vaccine formulation 2 given as an intramuscular injection

BIOLOGICAL

C. difficile vaccine formulation 3.

C. difficile vaccine formulation 3 given as an intramuscular injection

OTHER

Saline Placebo.

0.9% sodium chloride solution given as an intramuscular injection

Sponsors & Collaborators

• Pfizer

  lead INDUSTRY

Principal Investigators

• Pfizer CT.gov Call Center · Pfizer

Study Design

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

TRIPLE

Model

PARALLEL

Eligibility

Min Age

50 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2023-03-23

Primary Completion

2031-06-19

Completion

2031-06-19

FDA Drug

Yes

Countries

• United States

Study Locations