Management of Hepatitis B virus infection in patients on treatment with immunosuppressants or immunomodulators: Position Paper of Associazione Italiana Studio del Fegato (AISF), Associazione Italiana di Oncologia Medica (AIOM), Gruppo Italiano per il Trapianto di Midollo Osseo (GITMO), Società Italiana di Reumatologia (SIR), Società Italiana Trapianti d'Organo (SITO), Società Italiana di Gastroenterologia (SIGE), Società Italiana di Malattie Infettive e Tropicali (SIMIT)

Immunosuppressants and immunomodulators are increasingly used for the treatment of several oncologic and immune-mediated diseases. However, reducing or inhibiting the immune system's activity can interfere with the natural mechanisms responsible for Hepatitis B Virus (HBV) control and may potentially induce HBV reactivation (HBVr) in both Hepatitis B surface Antigen (HBsAg) positive patients (overt infection) and HBsAg negative/anti-Hepatitis B core (anti-HBc) positive carriers. Among factors contributing to the persistence of HBVr risk are insufficient awareness, the significant rate of patients not tested for HBV markers before immunosuppression/immunomodulation and the shortcomings in the correct management of anti-HBV therapy or prophylaxis. The risk of HBVr is influenced by the mechanism of action and the duration of immunosuppressants and immunomodulators, the underlying disease for which these drugs are used, and the virological patient's profile. However, HBVr can be prevented by the identification of at-risk patients through HBV screening in order to start anti-HBV therapy or prophylaxis. Following the need to have updated recommendations, primarily targeted to the Italian setting, on the management of HBV in patients on immunosuppressive and immunomodulator therapies, AISF, together with all the Scientific Societies mainly involved in their management, has promoted the drafting of a new dedicated document based upon available evidence at August 2025