LAUSR

GOALS Characterize and compare the risk of Clostridioides difficile infection (CDI) and cytomegalovirus colitis (CMVC) after initiation of vedolizumab or anti-tumor necrosis factor (TNF)α agents for ulcerative colitis (UC). BACKGROUND Immunosuppression is a risk factor for gastrointestinal infections including CDI and CMVC among patients with UC; however, the risk according to the biological class is poorly understood. STUDY A retrospective cohort study of adults with UC involving the initiation of vedolizumab or anti-TNFα agents during June 1, 2014 to December 31, 2020 was conducted at a large academic health system. The primary outcomes for both CDI and CMVC analyses were first CDI or CMVC after biological initiation. The secondary outcome for the CDI analysis was severe CDI (>10,000 white blood cells or serum creatinine >1.5 mg/dL). Independent variables included demographics and UC history/severity factors. Inverse probability of treatment weighted Cox regression was performed to assess the hazard of CDI by biological group. Due to few outcomes, CMVC was reported descriptively. RESULTS A total of 805 UC patients initiated vedolizumab (n=195) or anti-TNFα agents (n=610). There were 43 CDIs and 11 severe CDIs over 1436 patient-years. The inverse probability of treatment weighted Cox regression demonstrated no association between CDI and vedolizumab versus anti-TNFα (hazard ratio 0.33, 95% confidence interval 0.05-2.03), but identified a significantly lower hazard of severe CDI for vedolizumab versus anti-TNFα (hazard ratio 0.10, 95% confidence interval 0.01-0.76). There were 5 cases of CMVC, all in the anti-TNFα group. CONCLUSIONS There was a lower adjusted risk of severe CDI but not total CDI associated with vedolizumab. CMVC was not observed after initiating vedolizumab. These findings may provide reassurance regarding the use of vedolizumab when also considering the risk of gastrointestinal infections.