To our knowledge, there is no AAHA standard for vaccinating horses, nor does the American Association of Equine Practitioners have a "standard" for vaccination. This should be discussed with your local veterinarian to obtain his or her input on the diseases of importance in your area. The diseases that we routinely vaccinate against are tetanus, eastern and western encephalomyelitis, and West Nile virus. These are the diseases that kill backyard horses. If your horse is campaigning and coming into contact with other horses, then we also recommend influenza, rhinopneumonitis, and strangles vaccinations. You may consider others such as rabies, equine protozoal myelitis, and Potomac horse fever if these are problems in your area.