To test the hypothesis that whole-virion would be more immunogenic than conventional split-virion or subunit vaccines and may be adaptable to the antigen-sparing strategy, an inactivated, monovalent infl uenza A (H5N1), whole-virion vaccine was prepared from a highly virulent strain A/Vietnam/1194/2004 strain by removing the polybasic amino acids at the cleavage site, making the virus no longer pathogenic. The seed virus was grown to a high titer in embryonated eggs, inactivated with formalin, and purifi ed. These viruses were then adjuvanted with aluminum hydroxide and used in a phase 1 trial (6) . The highest immune response of 78% seropositivity was observed in the group given 2× 10 μg HA, which is equivalent to that elicited by higher doses of nonadjuvanted (90 μg) or adjuvanted (30 μg) split-virion vaccines (16, 17) .