Figure 5.

At 0 and 14 days, BALB/c mice were immunized IM with PBS or 15 or 3 µg HA, or they were immunized ID with 3 µg HA of the influenza H7N9 split vaccine. Two weeks later, they were challenged IN with a lethal dose of wild-type A/AnHui/1/2013 H7N9 virus (5.0 × 10³ TCID₅₀ pfu). Body weight was monitored daily (n = 6), and pathological changes (n = 3) in the lungs were analyzed at 7 days after challenge (A, B, C, D, E).