Statistical analyses were performed using the paired t test for the comparisons of prevaccination and postvaccination Ab-binding levels and Bio-F10 Ab inhibition activities. The neutralization activity was compared using log 2 microneutralization assay (MN) [8] titers. The proportions of .2-fold increase in Ab level were compared by McNemar's test for paired binary outcomes. All P values were 2-sided, and P values ,.05 were considered to be statistically significant. The correlation between F10-like IgG Abs and MN titer against H5N1 in postvaccination serum samples (n 5 77) was analyzed by Spearman rank correlation coefficient analysis.