Randomization strategy for eligible children. For this study, IVIG was Gamunex (immune globulin intravenous [human] 10%; this was marketed by Bayer at the start of the study, and then by Talecris and finally by Grifols). Gamunex was given according to manufacturer’s guidelines by means of a rapid infusion protocol: Start at 0.02 mL/kg per minute (1.2 mL/kg per hour) × 15 min. If no adverse reaction, increase to 0.04 mL/kg per minute (2.4 ml/kg per hour) × 15 minutes. If no adverse reaction, increase to 0.08 mL/kg per minute (4.8 mL/kg per hour) × 15 minutes. If no adverse reaction, increase to 0.10 mL/kg per minute (6.0 mL/kg per hour) for duration. If patients cannot sustain a particular infusion rate, then infusion is run at the highest tolerated rate.