The Effectiveness of Recombinant Coagulation Factor IX With Recombinant Albumin (rIX-FP) in Severe Hemophilia B Patients

Inclusion Criteria: * Male patients with age ≥ 20 years old * Endogenous FIX activity ≤1 IU/dL, * At least 50 exposure days (EDs) with FIX products, * No detectable inhibitor to FIX or inhibitor history, * Had a minimum of 2 nontrauma-induced bleeding episodes (any type or location) treated in the 6 months preceding study entry, * The patient or patient's parents or legal authorized representative, as applicable, are capable to understand the study objectives and procedure, and sign the written consent, * Accept that the supply of Idelvion might be stopped once the study is completed, * Able to complete a diary during 12 months or 50 EDs, whichever comes first. Exclusion Criteria: * Currently participating in an interventional clinical trial, * Known hypersensitivity to any FIX product or hamster protein, * Known inhibitor to FIX or inhibitor history, * With other comorbidities which are not suitable for this study, at investigator's discretion, * Not able to compliant with the prophylactic treatment, * Lacking previous treatment and bleeding records.