Safety and immunogenicity of a subvirion inactivated influenza A/H5N1 vaccine with or without aluminum hydroxide among healthy elderly adults

A total of 600 healthy adults ≥65 years were randomized to receive 2 vaccinations 1 month apart of a subvirion avian influenza A/H5N1 vaccine containing 3.75, 7.5, 15, or 45 μg of hemagglutinin (HA) with or without aluminum hydroxide (AlOH). All formulations were safe. Groups given the vaccine with AlOH had more injection site discomfort. Dose-related increases in antibody responses were noted after the second vaccination. Antibody responses to the vaccine were not enhanced by AlOH at any HA dose level. A microneutralization titer ≥40 was observed in 36% and 40% of subjects who received 45 μg of HA with or without AlOH, respectively.