Figure 2. NM2e protein immunization schedule.

The indicated mice were immunized intramuscularly with NM2e protein with or without adjuvant, three times at 2-week intervals. Blood was collected on days 14, 28, and 38, respectively. The immunized mice were challenged with influenza A virus PR8 at 20-fold the LD₅₀ on day 38. Body weight and survival were monitored for 3 weeks, until day 59.