Overall and Comparative Risk of Herpes Zoster With Pharmacotherapy for Inflammatory Bowel Diseases: A Nationwide Cohort Study.

BACKGROUND & AIMS Patients with inflammatory bowel disease (IBD) might be at increased risk for herpes zoster infection. We sought to quantify the risk of herpes zoster in patients with IBD and evaluate the effects of IBD and IBD medications on the risk of herpes zoster. METHODS We conducted 2 retrospective studies of populations of Veterans, from January 2000 through June 2016. In study 1, we compared the incidence of herpes zoster among patients with IBD receiving 5-ASA alone vs matched patients without IBD. In study 2, we compared the incidence of herpes zoster among patients with IBD treated with only 5-ASA, with thiopurines, with antagonists of tumor necrosis factor (TNF), with a combination of thiopurines and TNF antagonists, and with vedolizumab. We used multivariable Cox regression to estimate the hazard ratios and 95% CIs for herpes zoster associated with IBD in study 1 and with different treatments in study 2. We also estimated the incidence rate of herpes zoster based on age and IBD medication subgroups. RESULTS Compared to no IBD, ulcerative colitis (UC) and Crohn's disease (CD) were each associated with significantly increased risk of herpes zoster infection. In multivariable Cox regression (compared to no IBD), UC, CD, or IBD treated with 5-ASA treatment alone was associated with significantly increased risk of herpes zoster, with adjusted HRs (AHR) of 1.81 for UC (95% CI, 1.56-2.11), 1.56 for CD (95% CI, 1.28-1.91), and 1.72 for treated IBD (95% CI, 1.51-1.96). In multivariable Cox regression analysis, compared to exposure to 5-ASA alone, exposure to thiopurines (AHR, 1.47; 95% CI, 1.31-1.65) or a combination of thiopurines and TNF antagonists (AHR, 1.65; 95% CI, 1.22-2.23) was associated with increased risk of herpes zoster. However, exposure to TNF antagonists alone (AHR, 1.15; 95% CI, 0.96-1.38) was not associated with increased risk of herpes zoster. The incidence rates of herpes zoster in all age groups and all IBD medication subgroups were substantially higher than that in the oldest group of patients without IBD (older than 60 years). CONCLUSIONS In 2 retrospective studies of Veteran populations, we associated IBD and treatment with thiopurines, alone or in combination with TNF antagonists, with increased risk of herpes zoster. With the approval of a new and potentially safer vaccine for herpes zoster, the effects of immunization of patients with IBD should be investigated.