FIG. 4.

Protection of mice from lethal PR8 and WSN challenge. At week 4 after the final immunization, naïve and immunized mice were intranasally infected with a lethal dose of mouse-adapted PR8 or WSN virus (10× LD₅₀) (six mice per group). Mice were monitored daily for 15 days. (A and B) Percent survival after PR8 challenge (A) or WSN challenge (B); (C and D) body weight changes (in grams [G]) after PR8 challenge (C) or WSN challenge (D). Immunization groups are described in the legend to Fig. 2, and PR8 and WSN denote a challenge infection with PR8 and WSN, respectively.