By Brenda Jackson
As we’ve all learned during the recent pandemic, a vaccination “increases resistance to diseases that are endemic to a region…with potential public health significance…” They are often made from a weakened or killed version of the virus, bacteria or toxin in order to induce an immune response without causing illness. For that very reason, there are specific vaccines you should be administering on an annual basis to your horse(s), often called core vaccines, and then there are others that are more risk based, depending on environmental conditions, that can be skipped unless recommended by your veterinarian.
Core Vaccines – Adult Horses
1. Rabies
Rabies is a neurological disease not often occurring in horses but when it does, it is invariably fatal. Exposure can occur from the bite of an infected animal like racoon, bat, skunk, etc. Being curious animals, bites will often occur on the muzzle, face (when they bend down to inspect the curious creature) or on the lower legs. Most states require that the rabies vaccine be administered by or under the supervision of a licensed veterinarian to be considered valid. Adults should receive a rabies vaccination annually with pregnant mares receiving the vaccine within 4-6 weeks before foaling.
If you suspect a rabies exposure, contact your local veterinarian about protocols related to repeat vaccination or observation periods as well as reporting requirements to state public health officials.
2. Tetanus
Clostridium tetani spores are present in the soil as well as the intestinal tract and fecal material of horses and many other animals, including humans. Tetanus results from a neurotoxin released by the spore and is often fatal. The spores can survive in the environment for many years, so exposure risk never really goes away. This is not a contagious disease but one that can infect punctures, lacerations, exposed foal umbilicus or the exposed reproductive tract of the post-partum mare (retained placenta, for example). Previously vaccinated adults should receive annually with pregnant mares receiving the vaccine within 4-6 weeks before foaling. If the last dose was given more than 6 months from the date of injury or surgery, a booster is recommended. In adults previously unvaccinated, a 2-dose series is recommended with a 4-6-week interval between doses. Pregnant mares should be vaccinated 4-6 weeks prior to foaling.
3. Eastern & Western Equine Encephalomyelitis (aka EEE and WEE)
Transmission of this disease is mainly by mosquitoes and the impact carries a high mortality rate in horses. In the event of a disease outbreak, and ELISA test would be required to differentiate vaccinated animals from those that carry the virus.
Previously vaccinated adults should be boosted annually, preferably in the spring prior to onset of mosquito season, with pregnant mares being vaccinated 4-6 weeks before foaling. Unvaccinated adults should get a 2-dose series, with the 2nd dose being given 4-6 weeks after the first.
4. West Nile Virus (WNV)
WNV is the leading cause of insect-induced (most often the mosquito) encephalitis in both horses and humans in the U.S. While fatality is ~33% in horses, those that do survive may have residual effects because of the disease. Like EEE & WEE, give WNV vaccinations annually, in the spring prior to the onset of mosquito season. Pregnant mares should receive the WNV vaccine 4-6 weeks before foaling. For animals at high risk of infection, more frequent vaccination may be needed, under the recommendations of your local veterinarian. Some horses that have recovered from WNV may have life-long immunity but this is unconfirmed and annual boosters may still be required.
Core Vaccines – Foals
1. Rabies – if the parent mare is unvaccinated, give 1 dose at 4-6 months of age and repeat annually. If the parent mare was vaccinated give a 2-dose series with the first at 4-6 months of age and the second 4-6 weeks after the first.
2. Tetanus – 3 dose series in foals. If the parent mare is unvaccinated, 1st dose at 3-4 months, 2nd 4-6 weeks later and the 3rd at 10-12 months of age. If the parent mare is vaccinated, 1st dose at 4-6 months of age, 2nd 4-6 weeks later and the 3rd at 10-12 months of age.
3. Eastern & Western Equine Encephalomyelitis – Whether the parent mare is vaccinated or unvaccinated, give the 1st dose at 4-6 months of age, 2nd 4-6 weeks after that and the 3rd at 10-12 months of age.
4. West Nile Virus – Whether the parent mare is vaccinated or unvaccinated, give the 1st dose at 4-6 months of age, 2nd 4-6 weeks after that and the 3rd at 10-12 months of age. In the Southeast, your veterinarian may recommend an additional dose at 2-3 months of age if the event of an early mosquito presence.
Risk Based Vaccines

Printed with permission of the American Association of Equine Practitioners, https://aaep.org/guidelines/vaccination-guidelines/core-vaccination-guidelines