We read with interest the recent paper by Cannatelli et al 1 describing the adverse events (AEs) following COVID-19 vaccination from a large inflammatory bowel disease (IBD) cohort, which showed that patients with IBD had a similar rate of reported AEs to the general population but with a slightly higher rate of self-limiting gastrointestinal symptoms. However, the effects of COVID-19 vaccine on IBD activity, particularly severe flare resulting in hospitalisation and the interplay with the use of immunotherapy remain unknown. To address these questions, we analysed the territory-wide electronic medical records with vaccination linkage database in Hong Kong2–7 to examine the association between BNT162b2 vaccination and IBD flare.

From 4 161 762 patient records with affirmed vaccination status between 6 March 2021 and 30 September 2021, we identified 941 patients with IBD with two completed doses of BNT162b2, and 1196 unvaccinated IBD controls (online supplemental figure 1). Vaccine recipients were younger and less likely to have pre-existing chronic diseases. Approximately half of these patients with IBD received immunosuppressants and more than 20% were treated with biologics in the recent year. After inverse propensity treatment weighting, all variables were well balanced between vaccinated and unvaccinated groups (online supplemental table 1).

[gutjnl-2021-326860supp001.pdf]

During a median follow-up of 60 days among two-dose BNT162b2 recipients, six patients (onset time: 24 –103 days) had unplanned hospitalisation due to IBD (mean hospitalisation duration: 5.3±3.5 days). The number of unplanned IBD-related admissions in the unvaccinated group was 13 with a median follow-up of 69 days. Two-dose BNT162b2 vaccine was not associated with unplanned IBD hospitalisation (adjusted incidence rate ratio (aIRR): 0.69, 95% CI 0.35 to 1.36), all-cause hospitalisation (aIRR: 0.86, 95% …