A phase III randomized clinical trial in proportion 2:1 in favor of oral vancomycin (experimental treatment), multicentric, national, double-blinded, controlled with placebo. The main objective is to evaluate the effectiveness of treatment with oral vancomycin to reduce the incidence of Clostridioides difficile infection (CDI) in patients who suffered previous CDI and who need further hospitalization and treatment with systemic antibiotic therapy in the 90 days after the first CDI.

As secondary objectives the investigators intend to:

• Evaluate the effectiveness of the treatment with oral vancomycin as part of the prophylaxis arsenal to prevent ICD in patients with previous ICD episodes stratified by the number of previous recurrences.
• Compare the severity of recurrences in both study groups.
• Compare the effectiveness of the treatment with oral vancomycin depending on the type of systemic antibiotic therapy prescribed.
• Evaluate the tolerance and the safety of the treatment with oral vancomycin in terms of secondary effects and difficulty in therapeutic compliance.
• Evaluate if the treatment with oral vancomycin has an effect in diminishing the severity of ICD recurrences.

Inclusion Criteria:

• Age equal or superior to 18 years
• Previous history of Clostridioides difficile infection in the 90 days before the study enrolment
• Need for hospitalization and need of antibiotic therapy
• Signature of informed consent

Exclusion Criteria:

• Woman of childbearing age, pregnant woman, or breastfeeding woman
• Hypersensitivity to vancomycin
• Inability to comply with study protocol
• Critically ill condition or life expectancy less than 30 days
• Patients with diagnosed inflammatory bowel disease or with any conditions that produce chronic diarrhea
• Fulfilment of the criteria for diarrhea or diagnosis of CDI at the time of assessment for eligibility or in the previous 3 days
• Therapy with oral vancomycin or any other agent with activity against C. difficile for >48 hours in the previous 3 days;.
• Prophylaxis with oral vancomycin or any other agent with activity against C. difficile within the 70 days before the assessment for eligibility
• Systemic antibiotic therapy for 72 hours or more before the recruitment
• Ongoing enrolment in another RCT evaluating the effectiveness of other drugs
• Estimated use of systemic antibiotic therapy for more than 4 weeks

All IPD that underlie results in a publication will be shared

Data generated by the research will be made available as soon as possible, wherever legally and ethically possible. It is Planned to share data starting 9 months after publication, and data will be available for 24 months thereafter.

IPD will be shared with investigators whose proposed use of the data has been approved by an independent review committee identified for this purpose. Proposals should be directed to rafael.san@salud.madrid.org. To gain access, data requestors will need to sign a data access agreement.