Phase 3, Prospective, Multi-center, Open Label Study to Investigate Safety, Immunogenicity and Hemostatic Efficacy of PEGylated Factor VIII (BAX 855) in Previously Untreated Patients (PUPs) < 6 Years With Severe Hemophilia A (FVIII < 1%)

• Participant is \<6 years old at the time of screening.

• Participant is previously untreated with \<3 exposure days (EDs) to ADVATE, BAX 855 or plasma transfusion at any time prior to screening.

• Participant has severe hemophilia A (Factor VIII (FVIII) \<1%) as determined by the central laboratory, or a historical FVIII level \<1% as determined at any local laboratory, optionally supported by an additional FVIII gene mutation consistent with severe hemophilia A.

• Participant is immune competent with a cluster of differentiation 4 (CD4+) count \> 200 cells per cubic millimeter (mm\^3), as confirmed by the central laboratory at screening.

• Parent or legally authorized representative is willing and able to comply with the requirements of the protocol.

∙ Additional inclusion criteria for Part B (immune tolerance induction \[ITI\]).

• Parent or legal representative has/have voluntarily provided signed informed consent for ITI portion.

• Participant has a confirmed positive high titer inhibitor (\> 5.00 Bethesda unit (BU)) or has a positive confirmed low titer inhibitor (greater than or equal to \[\>=\] 0.6 BU) as determined by the central laboratory based on a second repeat blood sample with

‣ poorly controlled bleeding despite increased BAX 855 doses, or

⁃ requires bypassing agents to treat bleeding.