Immunogenicity and clinical protection against equine influenza by DNA vaccination of ponies

► DNA vaccines expressing the HA gene of equine H3N8 influenza virus were generated. ► DNA vaccines elicit homologous and heterologous immune responses after 3 vaccinations. ► DNA vaccines protect against disease and viral replication following H3N8 challenge. ► Needle-free delivery is as efficient and effective as conventional needle/syringe. ► DNA vaccines are a safe, effective alternative for veterinary vaccines against flu.