A.R. has received research grant support to institution from CSL Behring, Shire HGT, Pharming, Stallergenes, BioCryst, and Teva. D.L. is a researcher, speaker, and consultant to CSL Behring, speaker to Takeda, and consultant to BioCryst. H.L. has received grant support, personal fees, and nonfinancial support from CSL Behring during the conduct of the trial, grant support from BioCryst and Takeda, personal fees from Adverum, BioCryst, Pharming, and Takeda, travel support from CSL Behring, and nonfinancial support from Pharming and Takeda. M.C. received grants from Shire and personal fees from Alnylam, BioCryst Pharmaceuticals, CSL Behring, Dyax, KalVista, Pharming Technologies, Shire, Sobi (Swedish Orphan Biovitrum), and ViroPharma. T.C. reports grant support from CSL Behring during the conduct of the trial. He is a speaker to CSL Behring, Takeda, and Grifols, a consultant to CSL Behring, Takeda, and BioCryst. He has received research support from CSL Behring, Takeda, and BioCryst. P.K.K. reports grant support from AstraZeneca, CSL Behring, Genentech, and Shire. All other authors declare no competing interests.