Disclosed herein are nanoparticles comprising chitosan and an inactivated influenza A virus (IAV) antigen, wherein the chitosan encapsulates the inactivated IAV antigen. In some embodiments, the nanoparticle further comprises tripolyphosphate. In some embodiments, the nanoparticle reduces nasal shedding of an influenza A virus. In some embodiments, the nanoparticle elicits an increased amount of IgA antibody in a subject. Also disclosed are methods of reducing transmission of an influenza A virus, and methods of eliciting an immune response against an influenza A virus, in a subject compared to a control comprising administering to the subject a nanoparticle comprising chitosan and an inactivated influenza A virus (IAV) antigen, wherein the chitosan encapsulates the inactivated IAV antigen.
