Figure 5.

Immunoglobulin G avidity index of plasmablast-derived polyclonal antibodies (PPAbs) to the H1 protein in repeated trivalent inactivated influenza vaccine (TIV) receipt. PPAbs from the recipients after each annual vaccination were analyzed by an enzyme-linked immunosorbent assay (ELISA) in the presence or absence of 7 M urea, using a recombinant H1 protein from the H1N1 vaccine component strain of A/California/7/2009 (H1N1) as the detecting antigen. The avidity index is defined as [ELISA area under the curve with urea]/[ELISA area under the curve without urea]. The means and standard deviations are indicated with horizontal bars and vertical brackets. See Supplementary Figures 5 and 6–9 for details of statistical analysis.