Enteral Vancomycin as Primary Prophylaxis Against Clostridioides Difficile Infection in Critically Ill Patients

The goal of this clinical trial is to determine if oral vancomycin can prevent C.diff infection in adults who are critically ill and are at high risk of C.diff infection due to their medical conditions and being in the hospital. It will also help us learn about the safety of the drug in this setting. The main questions the trial aims to answer are: * Does oral vancomycin lower the rate of C.diff infection in high-risk patients? * Does C.diff carrier status change the C.diff infection rate as well as clearance of carrier status when vancomycin is used as primary prophylaxis? Researchers will compare the oral, active drug vancomycin to a placebo (a look-alike substance that contains no drug) to determine if vancomycin works to prevent C.diff infection in the hospital. Participants will: * Take oral vancomycin or a placebo while they receive systemic antibiotic(s) for up to five days after the last dose of said systemic antibiotic(s). The treatment of said systemic antibiotic(s) is not to exceed 21 days. * When discharged from the hospital, participants will continue to take the study medication in the event he/she did not complete the intended course of the study medication while in the hospital. * Participants will provide stool sample or rectal swabs for to assess their C.diff carrier status as well as any change in stool microbiome status, including VRE (vancomycin resistant Enterococcus) * After completion of the intervention period, participants will be contacted via telephone to assess if they developed diarrhea or any untoward effects of study medication.