The early detection of the T-cell response at day 8 postvaccination with the PAV3-HA vaccine suggest that it may be a good candidate for immediate administration just prior or following a suspected exposure to H5N1 virus. The success of rapid vaccination regimen was evaluated in two parts: first, overall survival and second, total viral load in lung tissue, as determined by TCID50 assay. BALB/c mice were challenged with a lethal dose of H5N1-H05 virus at 5, 8 and 10 days post-vaccination and lungs were harvested at day 3 post-infection. Although mice challenged 5 days post-vaccination did not survive lethal challenge (Figure 4a Survival was also assessed in groups of 10 BALB/c mice vaccinated with 10 8 , 10 9 , or 10 10 virus particles of recombinant adenovirus PAV3-HA or AdHu5-HA by intramuscular (I.M.) administration, challenged 28 days later with lethal homologous H5N1-H05 virus. Protection against clinical signs of disease with minimal weight loss and full survival was observed at the 10 10 vp/ mouse dose for both Ad-based vaccines ( Figure 5 ). Complete survival was also observed for both vaccines at a dose of 10 9 vp/ mouse, with the PAV3-HA vaccinated mice either asymptomatic or having milder signs of disease (14% weight loss) compared to AdHu5-HA (21% weight loss). Another desirable characteristic that influenza vaccines should provide is long-term protection. Therefore, long term immunity was evaluated in mice challenged 12 months after vaccination in order to determine whether protective immune responses could be maintained. PAV3-HA afforded full protection in mice challenged with 100 LD50 of H5N1-H05 virus 12 months post-immunization whereas 50% of mice vaccinated with AdHu5-HA succumbed (Figure 6a ). Higher HI antibody titers for PAV3-HA compared to AdHu5-HA (186665 and 60623, respectively (p = 0.006)) may have translated directly to the improved survival observed with the PAV3-HA vaccine. NAB titers were 23615 and 10611 for AdHu5-HA (Figure 6b ). An ELISA assay was also performed to detect total IgG antibody titres against the H5N1-HA antigen. Serum was obtained from mice 25 days and 1 year post-vaccination, and unvaccinated control mice (Figure 6c ). Total antibody titers were significantly lower for both vaccines after 1 year. On average, higher levels of IgG antibodies were detected for the PAV3-HA vaccine, however the difference was not statistically significant compared to AdHu5-HA (p = 0.241).