FIG 4.

Protective efficacy of influenza A virus PB1, NP, and M1 vaccines against 1.7 LD₅₀ of PR8. Fifteen groups of mice were immunized with the vaccine control (A), NP (B), PB1 (C), M1 (D), or a combination of the NP, PB1, and M1 (E) DNA, rVV, or prime-boost DNA-rVV vaccines (Table 1) at the times indicated in Fig. 3. Mice were challenged with 1.7 LD₅₀ of influenza virus PR8 at week 8 and were monitored daily for 17 days after challenge (n = 10 mice/group). The mice were weighed daily to detect morbidity (left graphs). The mean weights in each treatment group were followed for the duration of the study, and the percentage of the original body weight was calculated based on the mean weight of each group at day 0. The survival rates (right graphs) were calculated following challenge.