Study of Different Formulations of a Clostridium Difficile Toxoid Vaccine Given at Three Different Schedules in Adults

Inclusion Criteria: * Aged 40 to 75 years on the day of inclusion * Informed consent form has been signed and dated * Able to attend all scheduled visits and to comply with all trial procedures * For a woman of childbearing potential, use of an effective method of contraception or abstinence from at least 4 weeks prior to the first vaccination until at least 4 weeks after the last vaccination * At risk for developing Clostridium difficile infection during the trial because of impending elective surgery or hospitalization within 60 days of enrollment, or current or impending residence in a long-term care facility or rehabilitation facility. Exclusion Criteria: * Known pregnancy, or a positive urine pregnancy test * Currently breastfeeding a child * Participation in another clinical trial investigating a vaccine, drug, medical device, or medical procedure in the 4 weeks preceding the first trial vaccination * Planned participation in another clinical trial during the present trial period * Receipt of any vaccine in the 4 weeks preceding the first trial vaccination, except for influenza (seasonal or pandemic) and pneumococcal vaccine * Planned receipt of any vaccine in the 4 weeks following any trial vaccination, except for influenza (seasonal or pandemic) and pneumococcal vaccines * Previous vaccination against Clostridium difficile with either the trial vaccine or another vaccine * Current or prior Clostridium difficile infection (CDI) episode * Receipt of blood or blood-de…