Figure 4.

IgG responses after prime/boost vaccination and challenge. Serum samples collected on day 0, after the first vaccination (d21), on the day of challenge (d50), and 10 days post‐challenge (d60) were used for the determination of IgG titers. IgG ELISA was performed for sera of (A) vaccinated cotton rats and (B) nonvaccinated cotton rats. Cross‐reactive IgG against A/PR/8 H1N1 (C) and against X‐31 H3N2 (D) was measured in d50 serum samples. Titers are represented as log₁₀ titers with significance *P < .05 and **P < .01. LoD for the IgG titers is indicated at 2 with a dashed line. ELISA, enzyme‐linked immunosorbent assay; IgG, immunoglobulin; LOD, limit of detection; n.d, not determined; PBS, phosphate‐buffered saline; WIV, whole inactivated virus