Should Horses Get Vaccinated Seasonally?
Vaccination is one of the most important ways to protect your horse from several common illnesses. No matter what your horse's age, offering vaccinations at the right time will reduce the risk of serious illness.
Why Vaccines Are Important
Vaccines help the immune system recognize and fight germs that can cause certain illnesses and diseases. If a germ happens to enter your horse's body later, the immune system finds it and eliminates it. Vaccines prevent your horse from getting sick or make illnesses much less severe. Vaccinating your horse can also prevent the spread of illness to humans.
The American Association of Equine Practitioners separates vaccines into core and non-core types. Core vaccines are intended for all horses and target diseases or illnesses that occur throughout the entire country. Core vaccines are given annually and protect your horse from:
- Rabies
- West Nile Virus
- Eastern and Western Equine Encephalomyelitis (EEE/WEE)
- Tetanus
Rabies kills almost all horses infected by the virus, while tetanus kills about 80% of unvaccinated horses, according to Mad Barn. West Nile Virus symptoms range from coordination problems to brain inflammation. EEE/WEE causes fever, muscle twitching, difficulty swallowing, seizures, paralysis and death in some cases.
Non-core vaccines are given to horses with specific risk factors. Horses that spend time among other equines at shows or competitions should receive the strangles, equine influenza, and equine herpesvirus vaccines. Fever, nasal discharge, coughing, and other symptoms can occur with these illnesses.
An article published in Vaccine in 2022 noted that there is no standard for equine vaccines worldwide. If your horse travels to other countries for events, vaccinating your horse with non-core vaccines protects traveling horses and those that remain at home.
Other vaccines are location-dependent. For example, if you live in an area where Potomac Horse Fever is common, your veterinarian may recommend this vaccination. Horses get Potomac Horse Fever when they swallow aquatic insects that carry a specific type of bacteria. The illness may cause high fever, diarrhea, swollen limbs, laminitis, and colic.
What's the Best Time for Vaccinations?
The immunity provided by vaccines doesn't last forever. Some vaccines provide protection for six months, while others offer immunity for a year or longer.
Timing is particularly important for vaccines that tend to occur at certain times of the year. West Niles Virus and EEE/WEE are transmitted by mosquitoes and often sicken horses in the spring and summer.
Mosquitoes begin to hatch as the weather gets warmer. As you never know when warm weather will begin, it makes sense to vaccinate your horse in the early spring before mosquitoes hatch. If you live in a warmer area with a longer mosquito season, your veterinarian may recommend a vaccine booster in the late summer to ensure your horse is protected year-round.
Spring is the ideal time to offer several non-core vaccines. Since horse show season begins in the spring in many areas, vaccinating your horse against strangles, equine herpesvirus, and equine influenza in March or April ensures your horse is fully protected before competing.
Potomac horse fever tends to sicken horses in the summer and early fall. Vaccinating your horse in the late spring may offer the best protection.
Need to vaccinate your horse this spring? Contact our office to schedule a visit with the veterinarian.
Sources:
American Association of Equine Practitioners: Vaccinations for Adult Horses, 2026
https://aaep.org/wp-content/uploads/2020/05/Revised-Adult-Horse-Vaccine-Chart-FINAL-2026.pdf
Mad Barn: Tetanus in Horses, Signs, Prevention & Treatment, 2/22/2026
https://madbarn.com/tetanus-in-horses
Center for Equine Health School of Veterinary Medicine University of California, Davis: 10 Things You Might Not Know About Equine Vaccines, 4/27/2021
https://cehhorsereport.vetmed.ucdavis.edu/news/10-things-you-might-not-know-about-equine-vaccines
PetMD: Horse Vaccines: Which Vaccines Does My Horse Need?, 1/29/2025
https://www.petmd.com/horse/horse-vaccines
US Equestrian: Hagyard Equine Medical Institute: Dr. Ernie Martinez Talks You Through Core Vaccines and Risk-Based Vaccines, 9/5/2018
https://www.usef.org/media/newsletters/vaccines-good-investment-for-healthy-horse
PubMed: Vaccines: Equids' Core Vaccines Guidelines in North America: Considerations and Prospective, 3/4/2022