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.
Notably, in both trials the unadjuvanted vaccine elicited HAI titers ≥ 40 in >82% of subjects at a dose of 45 µg, which would fulfill CBER criteria for accelerated approval. The unadjuvanted vaccine also elicited HAI titers ≥40 in more than 52% of subjects against the drifted virus.
Gregory Glenn, M.D., Novavax' Senior Vice President and Chief Medical Officer, stated, "We have reviewed the preliminary top-line results of these trials and believe that achieving similar immune responses to our vaccine in future clinical trials, regardless of which of the two adjuvants is used, if any, would meet the immunogenicity criteria for accelerated approval of a pandemic influenza vaccine set by CBER. These data would also fulfill immunogenicity criteria set forth by the European Medicines Agency." Dr. Glenn added, "The response measured to the drift variant antigen is especially encouraging as the data suggest that our vaccine can be protective when the vaccine strain did not perfectly match a pandemic virus strain, which is an important consideration in the emergent response to a pandemic. We believe that with the results from these trials we have sufficient data to advance our avian influenza vaccine program into later-stage clinical testing."