Spring is here in Colorado, and with the temperatures rising so are the number of questions asking, “Wait.. which vaccines is my horse due for again?” Here we’ll review the core vaccines for adult horses based on current recommendations by the American Association of Equine Practitioners (AAEP), the schedule we administer these essential vaccines and the most important risk-based vaccines in Colorado.
Core vaccines are vaccines recognized by AAEP that have proven to safely and effectively protect horses from significant diseases threatening the equine population. AAEP and the American Veterinary Medical Association (AVMA) recommend that a series of these core vaccines be given annually to all adult horses, no matter where they live in the United States or what they are used for. The 5 core vaccines recommended by AAEP are:
- Rabies: This vaccine is extremely important as Rabies is 100% fatal and poses significant risk to all species, including humans. While Rabies is relatively uncommon in horses, the risk of disease is still present in Colorado. In fact, from 2019-2024, 522 animals tested positive for Rabies in our state alone. It’s important to note here that a Rabies vaccine must be administered by a veterinarian in order to be recognized by the Colorado State Department of Public Health.
- Tetanus: This prevents fatal infection from a neurotoxin produced by the bacteria Clostridium tetani, which can be found everywhere in the environment- soil, dust, manure, even the GI tract. It can be introduced into the body through wounds or punctures and is often fatal in affected horses.
- Eastern Equine Encephalitis (EEE) & Western Equine Encephalitis (WEE): This prevents viral encephalomyelitis (infection and inflammation of the brain and spinal cord) transmitted by mosquitoes that severely affects the nervous system of infected horses. The tetanus vaccine is also administered in combination with EEE/WEE.
- West Nile Virus (WNV): This prevents viral infection from mosquitoes that can leave affected horses with permanent neurologic side effects.
Risk-based vaccines are recommended by your veterinarian based on your horse’s environment, living/ traveling situation, exposure level, health status, occupation, and region. Available risk-based vaccines outlined by AAEP include Equine Influenza (EIV), Equine Herpesvirus (Rhinopneumonitis/ EHV-1 and EHV-4), Strangles, Anthrax, Botulism, Equine Viral Arteritis (EVA), Leptospirosis, Potomac Horse Fever, Rotaviral Diarrhea, Venezuelan Equine Encephalitis (VEE), and Snake Bites. The most important risk-based vaccines we typically recommend giving to adult horses in our area biannually are Equine Influenza and Equine Herpesvirus (Often referred to as a Rhino/ Flu vaccine).
- Equine Influenza: This is a common, highly contagious viral upper respiratory infection transmitted by aerosolized droplets from coughing or fomite transmission.
- Equine Herpesvirus (Rhinopneumonitis/ EHV-1 and EHV-4): This includes EHV-1 and EHV-4, both of which can infect the respiratory tract and lead to severe respiratory infections (rhinopneumonitis), and in some cases severe neurological disease (equine herpesvirus myeloencephalopathy, or EHM). EHV-1 can also cause abortion as well as fatal neonatal disease.
We ultimately tailor our vaccine protocols based on the individual needs of the horse as well as the core vaccines recommended by AAEP. Our recommended vaccine schedule at MVS ensures that horses are covered for all core vaccines as well as appropriate risk-based vaccines during the spring and fall. In the spring, we vaccinate for the insect-borne diseases (Eastern Equine Encephalitis, Western Equine Encephalitis, and West Nile Virus) as well as Tetanus, Equine Herpesvirus (Rhinopneumonitis) and Equine Influenza. In the fall, we vaccinate for Rabies and administer an additional Equine Herpesvirus (Rhino) and Equine Influenza (Flu) vaccine due to their highly contagious nature and relatively short duration of protection. Additional risk-based vaccines may be recommended by your veterinarian based on your horse’s individual needs and exposure risk. Foals, yearlings, and broodmares need multiple boosters of these vaccines to ensure adequate protection, so if you have young or pregnant horses be sure to consult your veterinarian regarding their unique vaccination schedules.
For horse and human alike, prevention is always the best medicine. Vaccinations are an essential component of your horse’s health and it’s important to consult with your veterinarian to ensure your horses are adequately protected from preventable diseases, through all seasons and stages of life. If you have any questions or concerns regarding your horse’s vaccinations or vaccination schedules, reach out to your veterinarian for guidance.
Click the following link to view the Colorado State University Equine Field Service Equine Vaccination Guidelines in an easy-to-read spreadsheet:
References:
Colorado Department of Public Health and Environment. (2025). Historical Rabies Data- Rabies
Prevalence Maps. Retrieved from
https://cdphe.colorado.gov/animal-related-diseases/rabies/rabies-data/historical-rabies-data
Colorado State University James L. Voss Veterinary Teaching Hospital. Equine Field Service.
Equine Vaccination Guidelines. Retrieved from
https://vetmedbiosci.colostate.edu/vth/services/equine-field-service/equine-vaccination-guidelines/
The American Association of Equine Practitioners Infectious Disease Committee. (2026).
Vaccinations for Adult Horses. Retrieved from:
https://aaep.org/guidelines-resources/vaccination-guidelines
Vaccination Information | Equine Disease Communication Center. Retrieved from: https://equinediseasecc.org
