Many VA patients are at-risk for complications from influenza because of advanced age and underlying chronic diseases. A more effective influenza virus vaccine is needed in older patient populations and high antibody levels are correlated with protection. Vaccine dose-sparing to maximize the number of doses available is a public health goal. The combination of influenza vaccine antigens with an adjuvant could help improve the vaccine. This study will be a phase 1, 2 randomized, observer-blind, multi-center, clinical trial, in patients aged 65 years and older, evaluating the immunogenicity and safety of a water-in-oil emulsion adjuvant (MAS-1) combined with each of three reduced influenza hemagglutinin (HA) antigen dose levels of trivalent influenza virus vaccine compared to unadjuvanted, standard dose trivalent influenza virus vaccine (TIV). Immunogenicity for each of the three viral strains (A/H1N1, A/H3N2, and B virus) in the concurrent seasonal influenza vaccine will be assessed. The hypothesis is that adjuvanted influenza virus vaccine (using reduced doses of influenza HA antigen containing 1 g, 3 g and 5 g of HA) has superior immunogenicity compared to unadjuvanted, standard dose trivalent influenza virus vaccine (containing 15 g HA antigen) for each of three viral strains, and the adjuvanted vaccine has an acceptable safety profile. The primary objectives are to demonstrate 1) acceptable safety for influenza virus vaccine, adjuvanted with MAS-1 compared to unadjuvanted, standard dose TIV, and 2) improved immunogenicity of the adjuvanted influenza virus vaccine compared to unadjuvanted, standard dose TIV for each of the three viral strains. Immunogenicity will be measured by hemagglutination inhibition (HAI) antibody titers. The primary measure of immunogenicity is the seroconversion rate at 1 month post-vaccination for each viral strain. Secondary and exploratory immunogenicity objectives include the seroprotection rate (defined as the proportion of subjects with a post-vaccination HAI antibody titer \> 1:40 for a viral strain) at 1, 3 and 6 months post-vaccination for each viral strain; the geometric mean titers (GMTs) of HAI antibody and ratio of GMTs pre-vaccination and at 1, 3 and 6 months post-vaccination between the four vaccine groups for each viral strain; and the geometric mean fold increase (GMFI) at 1, 3 and 6 months post-vaccination compared to pre-vaccination (i.e., GMT of the post-vaccination values divided by the GMT of the pre-vaccination value) for each virus strain within each of the four vaccine groups. The study population of 160 subjects (40 per vaccine group) who provide informed consent and meet eligibility criteria will be enrolled at four clinical sites. Subjects who meet the entry criteria for the study will be randomly assigned to receive one of the three adjuvanted influenza virus vaccine dose levels or unadjuvanted, standard dose TIV. Randomization will be stratified by clinical site (4 sites) and age (65-74 years old or 75 years old). Vaccine preparation will be performed at point-of-use by the site pharmacists according to a standardized procedure. Administration of vaccine will be performed by an unblinded vaccine administrator. Study assessments will be performed by blinded study personnel. Subjects will also be blinded to treatment assignment. Study subjects will each participate for a total of 12 months post-vaccination. The whole study duration of 32 - 32.5 months is expected to include 6 months of startup, 8 - 10 weeks of enrollment, 12 months of follow-up post-vaccination and 12 months of study closure and data analysis. If the objectives of this study are achieved and the hypothesis is correct, the adjuvanted influenza virus vaccine at one or more of the reduced HA antigen doses will induce an improved HAI antibody response compared to unadjuvanted, standard dose TIV with an acceptable safety profile. Results of this trial will inform the design of future clinical trials studying adjuvanted influenza virus vaccines utilizing this novel water-in-oil adjuvant emulsion that could include dose-finding studies for the optimal amount of adjuvant combined with one HA antigen dose, and larger phase 2 and 3 clinical trials.
