The primary objective of the study is to evaluate the safety of rFVIIIFc (BIIB031) in previously untreated participants with severe hemophilia A. The secondary objectives are to evaluate the efficacy of rFVIIIFc in the prevention and treatment of bleeding episodes in previously untreated patients (PUPs), to evaluate rFVIIIFc consumption for the prevention and treatment of bleeding episodes in PUPs, and to describe experience with the use of rFVIIIFc for immune tolerance induction (ITI) in participants with inhibitors.