A randomized, observer-blind, multicenter Phase 2 study tested six formulations of an H5N1 vaccine in healthy infants and children aged 6 months to under 9 years. The trial took place across Europe and Asia and included 420 children. Participants received vaccines containing different amounts of antigen and adjuvant, including standard or half standard adjuvant content.
Researchers measured immune responses at 3 weeks and 6 months after the second vaccination. They found that groups receiving the standard adjuvant content consistently showed higher antibody titers compared to other groups. All subjects achieved protective levels of MN titers, and 89.6% to 97.1% achieved higher MN titers across all vaccine groups.
Safety was monitored closely throughout the study. Adverse event rates were similar across all vaccine groups regardless of the antigen or adjuvant content used. No serious adverse events were reported, and the overall tolerability was acceptable. The data confirm that the vaccine formulation with 7.5 micrograms of HA plus 0.25 mL of MF59 is immunogenic with an acceptable safety profile in children.