Influenza is associated with 3,000-49,000 deaths in the US each year and vaccination is the best strategy for the prevention of influenza. A major obstacle to the development of widely effective influenza vaccines is the considerable antigenic variation across strains and types of influenza viruses. Influenza A H1N1 and H3N2 and influenza B viruses have co-circulated each season since 1977, and an updated trivalent vaccine has been required every year to protect against the most recent circulating strains. For Influenza B, it is particularly challenging to select a single strain for the licensed trivalent vaccine. Every season two antigenically distinct lineages of B strains (Yamagata and Victoria lineages) co-circulate worldwide; thus, there is often inadequate protection from the vaccine against influenza B. To address this issue, a quadrivalent vaccine, comprised of one H1N1, one H3N2, and two B antigens, will be offered for the 2013-2014 influenza season. The additional component should reduce the morbidity and mortality associated with influenza B infections. However, a quadrivalent vaccine will not solve many of the problems that persist with influenza vaccines such as (i) lack of vaccine efficacy due to mismatched vaccine strains (particularly for more deadly H3N2 and H1N1), (ii) no protection against pandemic viruses, and (iii) a continued requirement for annual update of the vaccine. Developing more universal vaccines, or even for the individual components of the vaccine, is essential for improving vaccine efficacy as well as pandemic preparedness. We have used a directed molecular evolution approach to identify novel variants of the influenza B hemagglutinin, or HA(B), that elicit cross- lineage activity to both Yamagata and Victoria viruses. Here, we propose to evaluate the feasibility of developing these lead HA(B) immunogens as a universal influenza B vaccine by analysis of the breadth of the protective response and serum neutralizing activity elicited by the lead variants. We will produce the HA(B) variants as virus-like particle vaccines and use them to immunize ferrets, which are a widely-used, highly relevant animal model for the study of influenza. Ferrets will be challenged with both lineages of influenza B to deter- mine if the HA(B) variant vaccines provide improved cross-lineage protection. In addition, we will extensively characterize the sera from immunized ferrets against a large panel of B viruses to assess the degree of inter- and intra-lineage neutralization breadth. Finally, we will carry out assays to learn if conserved epitopes in HA, such as epitopes near the receptor binding site or in the stem domain, are targeted by these vaccines. A single, widely-protective B component would be a significant and innovative advance for influenza vaccines. It would relieve constraints placed on manufacturing capacity and timelines as it could be produced year-round. Such a vaccine could eliminate the need for yearly vaccination against influenza B. Importantly, a universal B component would free up space in a quadrivalent vaccine for other, more deadly, components, particularly where pre-existing immunity is lacking (H2N2, H5N1, H7N9, etc.). Inclusion of these viruses in the seasonal vaccine could save lives in the face of a pandemic.