Herpes Zoster Incidence in Inflammatory Bowel Disease Patients: A Population-Based Study

Background: The aberrant immune response in inflammatory bowel disease (IBD) and immunosuppression may intrinsically predispose patients to infectious complications, such as herpes zoster (HZ). We quantified the incidence of HZ in IBD patients in the province of Quebec, Canada. Methods: We performed a descriptive study using the provincial "Regie de l'Assurance Maladie du Quebec" (RAMQ) health registry from 1996 to 2015. The study population consisted of all subjects in the source population who fulfilled the CD and UC case-defining criteria. HZ incidence rates (IRs) in person-years (py) were calculated according to age groups, sex, Charlson Comorbidity index (CCI), and IBD type. Age standardized incidence ratios (SIRs) were performed using the Quebec general population as reference. Results: A total of 39,366 patients met the diagnostic criteria of either Crohn's disease (CD; n = 23,388), ulcerative colitis (UC; n = 14,513), or IBD unclassified (n = 1465). We identified 2158 HZ cases. Crude IR was 6.67 cases/1000 py and 7.22 cases/1000 py for CD and UC patients, respectively. Unclassified IBD crude HZ IR was 7.54 cases/1000 py. No significant time trend was identified. HZ incidence is high in IBD patients > 50 years of age and among the very young (0-17 years of age; SIR, 3.38; 95% confidence interval, 2.64-4.26), especially females. Conclusions: These data suggest that HZ incidence is high in the IBD population. Preventives measures should be implemented in this at-risk population.