P559 SARS-CoV-2 vaccination does not increase the risk for flares in Inflammatory Bowel Disease patients

Rossier, L.(1)*;Seibold, F.(2);

(1)Intesto- Gastroenterology medical practice & Crohn-colitis center, Gastroenterology, Bern, Switzerland;(2)Intesto- Gastroenterology & Crohn-Colitis center- Fribourg and Berne- Switzerland, Gastroenterology, Bern, Switzerland;


Vaccination hesitancy is an important barrier to vaccination among inflammatory bowel disease (IBD) patients. The development of adverse events is the main concern reported. With this study we wanted to assess the SARS-CoV-2 vaccination safety by evaluating the post-vaccination flare risk and incidence of overall adverse events.


Surveys were distributed three consecutive months to each IBD patient coming in for a consultation in the Intesto Crohn & Colitis centre (Bern, Switzerland). Information about their vaccination-status and the occurrence of subsequent side effects was recorded. Their electronic medical record was then reviewed. Their baseline- and IBD- characteristics were transcribed as well as the dates of any flare occurring in 2021. These characteristics and the flare incidence were compared between the vaccinated and unvaccinated patients. Among the vaccinated population, the flare-risk was analysed at three different points in time: pre-vaccination, 1 month after any vaccination and over 1 month after any vaccination. Effect measurements according to Poisson models were applied. The characteristics of patients developing side effects were compared to those who did not.


396 IBD patients were enrolled, of which 91% were vaccinated, predominantly with mRNA vaccines. Throughout 2021, 85 flares were recorded with no difference between the vaccinated and unvaccinated groups.  Among the vaccinated group, there was no statistically significant difference between the flare-incidence in the pre-vaccination, 1 month after any vaccination and over 1 month after any vaccination subgroups as well as the Moderna- and Pfizer-subgroups. Overall, 37% patients reported side effects following any vaccination, mostly mild flu-like symptoms. More side effects were reported in the patients who were vaccinated with the mRNA-1273/ Spikevax (NIH-Moderna) vaccine in comparison with BNT162b2/Cominarty (Pfizer-BioNTech).


In this mono-centric study SARS-CoV-2 vaccination with mRNA vaccines seems safe with the occurrence of mostly mild side effects. The flare risk is not increased in the month following any vaccination.