Clostridium Difficile Vaccine 2-Dose Versus 3-Dose Study

Inclusion Criteria: * Evidence of a personally signed and dated informed consent document. * Willing and able to comply with study procedures. * Subjects with an increased risk of future contact with healthcare systems or subjects who have received systemic antibiotics in the previous 12 weeks. * Ability to be contacted by telephone during study participation. Exclusion Criteria: * Pregnant female participants; breastfeeding female participants; positive urine pregnancy test for women of childbearing potential (WOCBP); and WOCBP who are, in the opinion of the investigator, sexually active and at risk for pregnancy and are unwilling or unable to use effective methods of contraception as outlined in this protocol from the signing of the informed consent until at least 28 days after the last dose of investigational product. * Prior episode of CDI, confirmed by either laboratory test or diagnosis of pseudomembranous colitis at colonoscopy, at surgery, or histopathologically. * Participants who may be unable to respond to vaccination due to: * Metastatic malignancy; or * End-stage renal disease (glomerular filtration rate \<15 mL/min/1.73 m2 or on dialysis). * Any serious medical disorder that in the investigator's opinion is likely to be fatal within the next 12 months. * Congenital or acquired immunodeficiency. * Known infection with human immunodeficiency virus (HIV). * Any bleeding disorder or anticoagulant therapy that would contraindicate IM injection. * Any cont…