A phase I randomized, double-blind, controlled trial of 2009 influenza A (H1N1)inactivated monovalent vaccines with different adjuvant systems

We conducted a phase I, multicenter, randomized, double-blind, placebo-controlled, multiarm(10) parallel study involving healthy adults to evaluate the safety and immunogenicity of influenzaA (H1N1) 2009 non-adjuvanted and adjuvanted candidate vaccines. Subjects received two intramuscularinjections of one of the candidate vaccines administered 21 days apart. Antibody responses weremeasured by means of hemagglutination-inhibition assay before and 21 days after each vaccination. Thethree co-primary immunogenicity end points were the proportion of seroprotection >70%, seroconversion40%, and the factor increase in the geometric mean titer 2.5. A total of 266 participants were enrolled into the study. No deaths or serious adverse eventswere reported. The most commonly solicited local and systemic adverse events were injection-site painand headache, respectively. Only three subjects (1.1%) reported severe injection-site pain. Four 2009 influenza A (H1N1) inactivated monovalent candidate vaccines that met the three requirements to evaluateinfluenza protection, after a single dose, were identified 15 g of hemagglutinin antigen withoutadjuvant; 7.5 g of hemagglutinin antigen with aluminum hydroxide, MPL and squalene; 3.75 g ofhemagglutinin antigen with aluminum hydroxide and MPL; and 3.75 g of hemagglutinin antigen with aluminum hydroxide and squalene.Adjuvant systems can be safely used in influenza vaccines, including the adjuvant monophosphory lipid A (MPL) derived from Bordetella pertussis with squalene and aluminum hydroxide, MPL with aluminum hydroxide, and squalene and aluminum hydroxide.