Modified viruses injected into the horse to provide an immune response are known as what?

The term that refers to modified viruses injected into horses to provoke an immune response is vaccinations. Vaccinations are designed to introduce a harmless component or a weakened form of a pathogen into the body, prompting the immune system to recognize and fight off the disease if the horse is exposed to the actual pathogen in the future.

Vaccines often contain antigens derived from the virus or bacteria which stimulate the immune system; however, the process and product of injecting these antigens specifically for the development of immunity is what defines vaccinations. This method of introducing immunity helps in preventing diseases rather than just treating them, which underscores the importance of vaccinations in equine health management.

The other terms, while related to the immune system, do not accurately describe the process of using modified viruses for the purpose of inducing immunity: antibodies are proteins produced by the immune system in response to antigens; serums are blood components that contain antibodies; and antigens are the substances that trigger an immune response, but they are not the modified viruses used in vaccinations themselves.