What is this study all about?

Clostridium difficile (C. diff) is one of the most common causes of healthcare-related infections.

C. diff is a type of bacteria that lives in the human intestines and its spores can survive outside of the body for months. These spores are resistant to cleaning and are most commonly transmitted in healthcare settings. People can become infected by touching surfaces that are contaminated or by coming into contact with a healthcare worker that has the bacteria or spores on their hands.

People most at risk of getting sick due to C. diff are those who are taking antibiotics, being treated in a healthcare facility, the elderly and people who are already ill. This infection can cause symptoms that include frequent diarrhea, inflammation of the colon, fever, nausea and abdominal pain; in severe cases it can be life-threatening.

Your participation in this study is expected to last between 18 and 42 months and will require 5 office visits within the first 7 months. You will also receive periodic contact from the study team, including regular electronic reminders of your participation and routine telephone calls after 12 months and at the end of the study. If you have diarrhea 3 or more times within 24 hours, you will be asked to collect a sample of the diarrhea. We will provide a kit for this and arrange for a courier to collect the sample.

You will be randomly assigned (like the flip of a coin) to receive either the investigational study vaccine or a placebo. This product will be given to you by injection. The placebo looks like the study vaccine, but has no active ingredient in it. You will not know if you are receiving the active vaccine or the placebo.

The purpose of this trial is to evaluate the safety and efficacy of an investigational vaccine in reducing the chances of getting sick due to C. diff. The knowledge gained from this study may help others in the future.

Eligible participants will receive study related tests and procedures at no cost and compensation may be available.


  • Are 60 years old or over
  • Have had at least 2 visits to the emergency room, or had a hospitalization of at least 2 nights in the last 12 months, or
  • Have a planned hospitalization that will require a stay of 2 or more nights or
  • Are a resident in a nursing facility or
  • Have had at least 10 outpatient visits in the last 12 months or
  • Have received oral or injectable antibiotics within the last 12 weeks.
  • **Please note, other conditions may apply**