Objectives: The treatment of inflammatory bowel disease (IBD) has been revolutionized by the use of immunomodulatory agents. Although these potent drugs are effective in controlling disease activity, they also cause an increased risk of new infections or reactivation of latent infections. On these premises, we aimed to provide guidance on the definitions of immunocompromised patients, opportunistic infections and the risk factors associated with their occurrence in an IBD context, and to suggest the proper screening tests for infectious diseases and the vaccination schedules to perform before and/or during therapy with immunomodulators. Methods: All the most recent evidences - filtered by the combined work of gastroenterologists and infectious disease experts - were summarized with the aim to provide a practical standpoint for the physician. Results: A systematic screening of all infections which may arise during therapy with immunomodulator drugs is necessary in all patients with IBD. Conclusions: The ideal timing to perform screening tests and vaccinations is at the diagnosis of the disease, regardless of its severity at onset, because the course of IBD and its treatment may vary over time, and an immunocompromised status may hamper efficacy and/or possibility to perform all necessary vaccines. (C) 2017 The British Infection Association. Published by Elsevier Ltd. All rights reserved.