Protective efficacy of pre-pandemic IVIG and post-pandemic H-IVIG. To evaluate passive protection efficacy, SCID mice were intraperitoneally administered with 200 μl of pH1N1 hyperimmune IVIG (two lots, HI titer 1:1,280) or pre-pandemic IVIG (pool of five lots, HI titer 1:70) 3 days prior to challenge with 6×104 TCID50 of wild-type pH1N1 by intranasal instillation. The control group received 200 μl of PBS and survival was monitored for 29 days. Statistical differences between the IVIG group and the PBS control group, and between the IVIG group and the H-IVIG group, were calculated with a Log-rank (Mantel-Cox) test using the GraphPad Prism software. Abbreviations: d, days; n.s., not significant; IVIG, pre-pandemic intravenous immunoglobulin; H-IVIG, hyperimmune intravenous immunoglobulin.