Figure 2. Protection from influenza and secondary bacterial infection by NP vaccination.

Young (2-3 mos.) and aged (19-22 mos.) C57BL/6 mice were vaccinated with NP or PBS on days −31 and -21. On day 0, they were infected intranasally with 400 EID₅₀ of PR8 influenza. A. Weight loss and B. survival were monitored following infection. C. On day 0, NP (right graph) or PBS (left graph) vaccinated young and aged mice were infected intranasally with 400 EID₅₀ of PR8 influenza and then 5 dpi, infected with 250 CFU of Streptococcus pneumoniae and survival was monitored. Data shown is combined from 2 independent experiments with a total of 8 to 10 mice per group. *p < 0.05 by Student's t test comparing vaccinated and control groups; **p < 0.05 by Log rank test.