BAX 326 Pediatric Study

Main Inclusion Criteria: * Participant and/or legal representative has/have voluntarily provided signed informed consent * Participant has severe (FIX level \< 1%) or moderately severe (FIX level ≤ 2%) hemophilia B * Participant is \< 12 years old at the time of screening * Participant has no evidence of a history of FIX inhibitors (based on the participant's medical records) * Participant is immunocompetent as evidenced by a CD4 count ≥ 200 cells/mm\^3 Main Exclusion Criteria: * Participant has a detectable FIX inhibitor at screening, with a titer ≥ 0.6 Bethesda Unit (BU) * Participant has a history of allergic reaction, e.g. anaphylaxis, following exposure to FIX concentrate(s) * Participant has evidence of an ongoing or recent thrombotic disease * Participant has an inherited or acquired hemostatic defect other than hemophilia B