Secondary Prevention of Clostridioides Difficile Using Vancomycin

Re-exposure to systemic antibiotics (i.e., antibiotics absorbed into the bloodstream) is common after a Clostridioides difficile infection (CDI) and is the strongest risk factor for a recurrent episode. Oral vancomycin to prevent a recurrence during antibiotic re-exposure may reduce this risk but the data supporting this practice are limited. The aim of this trial is: 1\) Does oral vancomycin prophylaxis prevent CDI recurrences in patients with recent CDI (within 120 days) and who are re-exposed to systemic antibiotics? The trial will compare oral vancomycin to placebo. Participants will: * Take the study drug (either vancomycin or placebo) twice daily for the duration of systemic antibiotics plus once daily for 7 days after completion of systemic antibiotics. * Attend an in-person or over the phone follow-up at day 56 * Respond to weekly electronic questionnaires