Abstract:Seasonal influenza viruses (IAV) are a common cause of acute respiratory illness worldwide and generate a significant socio-economic burden. IAV rapidly mutate, necessitating annual vaccine reformulation as traditional vaccines do not typically induce broad-spectrum immunity. In addition to seasonal infections, emerging pandemic influenza viruses present a continued threat to global public health. Pandemic influenza viruses have consistently higher attack rates and are typically associated with greater mortality as compared to seasonal strains. Ongoing strategies to improve vaccine efficacy typically focus on providing broad-spectrum immunity, and while both B and T cells can mediate heterosubtypic responses, typical vaccine development will augment either humoral or cellular immunity. However, multipronged approaches, targeting several antigens, may limit the generation of viral escape mutants. There are few vaccine platforms that can deliver multiple antigens and generate robust cellular and humoral immunity. In this work, we describe a novel vaccination strategy, tested pre-clinically in mice, for the delivery of novel bivalent viral-vectored vaccines. Here, we show this strategy elicits potent T cell responses toward highly conserved internal antigens, whilst simultaneously inducing high levels of antibodies towards hemagglutinin (HA). Importantly, these humoral responses generate longlived plasma cells and generate antibodies capable of neutralising variant HA-expressing pseudotyped lentiviruses. Significantly, these novel viral-vectored vaccines induce strong immune responses capable of conferring protection in a stringent influenza A virus challenge.Thus, this vaccination regimen induces lasting efficacy toward influenza. Importantly, the simultaneous delivery of dual antigens may alleviate the selective pressure thought to potentiate antigenic diversity in avian influenza viruses.