FIG 2.

Humoral immune responses induced by vaccination. Blood was collected from the cranial vena cava of ferrets 4 weeks after each vaccination (day 28 and day 56). (A and B) Box-and-whiskers plot of antibody titers against the homologous antigen as determined by HI assay (A) and NI-ELLA (B). Black dots represent titers of individual ferrets, the box represents the interquartile range, the vertical line inside the box represents the median, and the whiskers extend to the highest and lowest observations. (C) Activity of the NA protein in vaccines measured by the ELLA assay.