Influenza hemagglutinin (HA) peptide is widely used in immunology and vaccine development. It serves as a key component in the design of influenza vaccines, helping to elicit an immune response against the virus. Researchers utilize HA peptides to study antibody binding and immune system recognition, which is critical for understanding viral infection mechanisms. Additionally, these peptides are employed in diagnostic assays to detect influenza-specific antibodies in patient samples. HA peptides also play a role in the development of universal flu vaccines, aiming to provide broader protection against various influenza strains. Their application extends to preclinical studies, where they are used to evaluate the efficacy of new antiviral therapies and vaccine candidates.