Figure 2.

Effect of a single immunization on clinical symptoms after virus challenge. Cotton rats mock‐immunized with PBS or immunized once with 0.5, 1, or 5 µg WIV and challenged on day 30 with 5 × 10⁷ TCID₅₀ of homologous A/Cal/Gro were followed for 3 days and weight (A‐D), temperature (E‐H), and respiration rate (I‐L) were recorded. Discontinued line with X symbol indicates dead animal. PBS, phosphate‐buffered saline; WIV, whole inactivated virus