Hematopoietic stem cell transplantation is an increasingly common treatment method for benign and malignant hematological diseases. However, infections
before and after transplantation are the most important causes of morbidity and mortality, working against the developments in diagnosis and treatment.
The regeneration of the immune system after stem cell transplantation spans a period of 12-18 months and the risk of bacterial, fungal, and viral infection
development is highest in the first 1-2 years after transplantation. While hepatitis B virus (HBV) reactivation is well defined in patients receiving immunosuppressive therapy in the literature, cases of acute viral hepatitis B (AVHB) development during immunosuppressive therapy are limited. Therefore, we present a
case of AVHB developing after immunosuppressive therapy in a patient who was immunized against the HBV vaccine.