Introduction: We aimed to assess the risk of serious infection in patients with inflammatory bowel disease (IBD) treated with vedolizumab compared with those treated with anti-tumor necrosis factors (TNF) and the general population.

Methods: In this Swedish cohort study, treatment episodes were identified from nationwide health registers. We used Cox regression with propensity score-matched cohorts to estimate hazard ratios (HRs) for incident serious infections, defined as infections requiring hospital admission.

Results: During 1,376 treatment episodes in Crohn's disease, the rate of serious infections per 100 person-years (PY) was 5.18 (95% CI = 3.98-6.63) with vedolizumab vs 3.54 (95% CI = 2.50-4.85) with anti-TNF; HR = 1.72 (95% CI = 1.12-2.65), partly explained by more gastrointestinal infections. Compared with the rate of 0.75/100 PY (95% CI = 0.59-0.92) in a matched general population cohort, vedolizumab demonstrated higher risk (HR = 7.00; 95% CI = 5.04-9.72). During 1,294 treatment episodes in ulcerative colitis, the corresponding rates were 3.74/100 PY (95% CI = 2.66-5.11) with vedolizumab vs 3.42/100 PY (95% CI = 2.31-4.89) with anti-TNF; HR = 0.80 (95% CI = 0.47-1.36) during the initial 1.1 years and HR = 2.03 (95% CI = 0.65-6.32) after 1.1 years (truncated due to nonproportional hazards). Pneumonia accounted for 40% of all infections among anti-TNF, whereas no case was observed among vedolizumab episodes. Compared with the rate of 0.69/100 PYs (95% CI = 0.53-0.87) in a matched general population cohort, vedolizumab showed an HR of 5.45 (95% CI = 3.67-8.11).

Discussion: Vedolizumab was associated with increased risks of serious infections compared with anti-TNF in Crohn's disease but not in ulcerative colitis. Nonetheless, the panorama of serious infections seemed to differ between the drugs. Our findings underscore the importance of clinical awareness of infections and the safety profile of the 2 therapies.