Equine influenza causes significant welfare harm in unvaccinated horses, and understanding optimal vaccination protocols improves both individual protection and herd immunity outcomes.
Equine influenza vaccination is one of the clearest examples of a preventive welfare intervention with strong evidence of benefit. The disease causes significant suffering — horses with influenza are systemically unwell, febrile, and unable to perform normal activities for weeks. Outbreaks in unvaccinated or undervaccinated populations can spread rapidly through competitions and shared facilities, causing welfare harm at scale. Proper vaccination protocols protect individual animals from preventable illness while contributing to herd immunity that protects the broader equine population. Vaccination hesitancy in the equine community, sometimes driven by concerns about post-vaccination reactions, should be addressed through veterinary education rather than reduction in vaccination rates, as the welfare costs of influenza far exceed those of any vaccine reactions.