Vaccines and vaccination to control equine influenza

Vaccination of horses against equine influenza virus has been employed for many years, and is the main element of control and prevention strategies for that disease. This chapter reviews the different types of vaccines for equine influenza, including vaccines already licensed for commercial use and also experimental vaccines applying modern technologies, together with their advantages and limitations. The criteria for measuring vaccine efficacy are described, including the animal models used for experimental efficacy studies, and the serological and cell-mediated immunological tests used to measure horses' immune responses to vaccination or infection. Factors that affect vaccine-induced protection are addressed, such as the correlation between serum antibody titers and protection from disease, induction of respiratory mucosal immunity, vaccination scheduling, and maternal antibody interference. The current international system for equine influenza surveillance and updating of the virus strains in vaccines is described.