To assess whether vaccinated animals would be protected against challenge infection with highly pathogenic H5N1 virus, specific pathogen-free (SPF) chickens at 4 weeks of age were immunized intramuscularly (i.m.)with adjuvant-free VSV*ΔG(HAH5-HP) particles using doses of 2×106, 2×107, or 2×108 ffu. Here, HP is linked to infection.