Objective: Influenza immunization is recommended for children with IBD, however safety concerns may limit uptake. This study assessed whether immunization was associated with adverse events in IBD patients using a population-based database of children with IBD.
Methods: All children <19 years diagnosed with IBD in Ontario, Canada between 1999-2009 were identified using health administrative data, and matched to non-IBD controls. Self-controlled case series (SCCS) analyses determined health services event rates (outpatient visits, hospitalizations and emergency visits) in any 2-week risk period to 180 days post-immunization compared to a no-risk control period. Relative incidence (RI) was calculated for overall and IBD-related events and rates were compared between IBD cases and controls using relative incidence ratios (RIR).
Results: A total of 4916 IBD patients were matched to 21 686 controls. IBD patients were more likely to have received immunization than controls (25.3% vs 13.2%, P < .001). No increased event rates existed in IBD cases during risk periods (pooled RI 0.95, 95% CI 0.84-1.07), including hospitalizations and emergency visits. There was a slightly higher event rate in IBD cases versus controls for days 3-14 (RIR 1.60, 95% CI 1.05-2.44, P = .03). IBD-related visit rates were lower in risk periods compared to control period (pooled RI 0.81, 95% CI 0.68-0.96).
Conclusions: There was no increase in health services use in the post-vaccine risk period in IBD patients, and there was evidence for a protective effect of influenza immunization against IBD-related health services use. Influenza immunization is safe in children with IBD and should be encouraged to improve poor coverage rates.
Keywords: epidemiology; health administrative data; inflammatory bowel diseases; influenza vaccines; pediatrics; seasonal influenza; vaccine safety.