The adjuvanted vaccines induced strong immunogenicity at all antigen doses tested, including the lowest (3.75 µg) dose, based on hemagglutination inhibition assay (HAI) responses against the vaccine virus at day 42.
- 88 to 100% of subjects receiving adjuvanted vaccine at all dose levels demonstrated serum HAI titers ≥40, a seroprotection level believed to be associated with reduced risk of disease.
- 86 to 100% of subjects receiving adjuvanted vaccine at all dose levels demonstrated seroconversion rates with either a four-fold rise in HAI titer or a titer of ≥1:40 from a negative baseline.
- Immune responses would fulfill U.S. Food and Drug Administration (FDA) Center for Biologics Evaluation and Research (CBER) seroprotection and seroconversion criteria for accelerated approval at the lower bound of the 95% confidence level.
- When tested against another avian A/H5N1 virus different from that in the vaccine, up to 80% of subjects receiving adjuvanted vaccine developed HAI titers ≥40 against the drifted virus.