IGHA1 and influenza: To complement the gold-standard HAI assay, which targets antibodies that can block receptor binding of the virus, we used Luminex multiplex technology and antibody characterization to generate a more in-depth analysis of influenza-specific serum antibodies that target a total of 10 different HA, NA, and NP proteins from various IAV and IBV strains to assess their isotype distribution (IgG1, IgG2, IgG3, IgG4, IgA1, IgA2, and IgM) and potential to engage with Fcγ receptors (FcγRIIa and FcγRIIIa) following influenza vaccination.