Protective efficacy of a trivalent recombinant hemagglutinin protein vaccine (FluBlok®) against influenza in healthy adults: A randomized, placebo-controlled trial

► Randomized, placebo-controlled, multicenter assessment of efficacy of baculovirus expressed hemagglutinin vaccine for prevention of laboratory-documented influenza illness in healthy adults. ► Vaccine was safe and generated serum hemagglutination-inhibiting antibody responses against all three components in the majority of recipients. ► Influenza infections during surveillance were antigenically mismatched to the components in the vaccine. ► Vaccine efficacy was 44.8% (95% CI, 24.4%, 60.0%) for prevention of preventing culture-confirmed influenza illness.