AbstractBackground and AimsA similar course of COVID-19 in patients with inflammatory bowel diseases [IBD] and in the general population has been reported. However, disease prevalence in IBD patients is presently unknown. In this prospective observational study, we aimed at determining SARS-CoV2 infection prevalence in IBD patients treated with biologic therapy.MethodsFrom IBD patients under biologic therapy and recruited from three different locations in Italy and Germany, 354 sera were evaluated for antibody presence by RBD ELISA. Control groups were: i] age-matched healthy subjects tested in the same time period in Milan, Italy; ii] healthy subjects collected in the pre-COVID era; iii] IBD patients under biologic therapy collected in the pre-COVID era.ResultsEight out of 354 patients tested positive for the anti-RBD-SARS-CoV2 IgG antibody [prevalence 2.3%]. The percentage of IgG-positive patients among those recruited from Milan was significantly higher than among those recruited from other locations [prevalence 5.4% vs 0.4%, p <0.005]. IgG-positive patients reported a significantly higher incidence of fever, anosmia, and ageusia, and were more likely to have entered into close contact with COVID-19-positive subjects before the study enrolment.ConclusionsSeroprevalence of SARS-CoV2 in IBD patients treated with biologic therapy reflects values measured in the local general population. Specific symptoms and contact history with SARS-CoV2-infected individuals strongly increase the likelihood of SARS-CoV2 seropositivity.