Clinical Research Directory

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

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 does not work. 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 clinic 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.

Secondary Prevention of Clostridioides Difficile Using Vancomycin

Re-exposure to systemic antibiotics (i.e., antibiotics absorbed into the bloodstream) is common after a Clostridioides difficile infection (CDI) and is the strongest risk factor for a recurrent episode. Oral vancomycin to prevent a recurrence during antibiotic re-exposure may reduce this risk but the data supporting this practice are limited. The aim of this trial is: 1\) Does oral vancomycin prophylaxis prevent CDI recurrences in patients with recent CDI (within 120 days) and who are re-exposed to systemic antibiotics? The trial will compare oral vancomycin to placebo. Participants will: * Take the study drug (either vancomycin or placebo) twice daily for the duration of systemic antibiotics plus once daily for 7 days after completion of systemic antibiotics. * Attend an in-person or over the phone follow-up at day 56 * Respond to weekly electronic questionnaires

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

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.