Equine Vaccination Do’s and Don’ts

Determining exactly which vaccines a horse needs can be confusing. Here are some basic do’s and don’ts to make sure you’re providing the disease protection your horse needs.

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Equine Vaccination Do
Work with your vet to develop a vaccination program individualized to each horse on your property. | Photo: Alexandra Beckstett/The Horse

Best practices for making sure your horse gets the disease protection he needs

Do I need to vaccinate my horse against leptospirosis? Does my retiree need the same shots as my performance horse? What happens if they miss a round of vaccines? Determining exactly which vaccines a horse needs can be confusing. Reviewing the guidelines set forth by the American Association of Equine Practitioners (AAEP) is a good place to begin your research, and talking with your veterinarian can help you make the best decision based on your horse’s lifestyle, age, and geographic location. In the meantime, we’ve distilled the topic down into some basic do’s and don’ts to make sure you’re providing the disease protection your horse needs.

Core Vaccines

DO have your horse vaccinated with all core vaccines, which are those the American Veterinary Medical Association and AAEP ­recommend for all horses, every year, regardless of location, gender, or age.

“There are no instances where horses should not be vaccinated with AAEP-­recommended core vaccines,” says ­Elizabeth Davis, DVM, PhD, Dipl. ACVIM, professor and head of the department of clinical sciences at Kansas State University’s College of Veterinary Medicine, in Manhattan. “The one exception is the situation where a horse has demonstrated a severe adverse reaction to a vaccine. This is a rare occurrence, but it can happen. When this happens, it is important to work with a veterinarian to determine the ideal course of action.”

The AAEP core vaccination list consists of rabies, Eastern and Western equine encephalomyelitis (EEE/WEE), tetanus, and West Nile virus (WNV). Establishing immunity against the pathogens that cause these diseases requires an initial priming series of vaccine doses, followed by an ­annual booster to maintain ­immunity.


Exposure to these life-­threatening mosquito-borne viruses varies from year to year. This vaccine has stayed on the core list because of high disease mortality rates (75-90% for EEE, 20-30% for WEE) and you can’t completely eliminate exposure. If your horse lives in an area where mosquitoes are common for more than six months of the year, vets recommend vaccinating twice yearly. Otherwise, an annual booster is sufficient.


This is another mosquito-borne virus with fluctuating annual case numbers depending on weather (and resulting mosquito populations) and vaccination vigilance. It’s fatal in 30% of cases, and even horses that recover from the acute phases of the illness often still demonstrate gait and behavioral abnormalities six months post-­diagnosis. If your horse lives in an area where mosquitoes are a threat more than six months of the year, vets recommend vaccinating twice annually. Horses under the age of 5 or over 15 are more susceptible to the disease and should be vaccinated more frequently if your veterinarian recommends it. For all other horses an annual booster is ­sufficient.


Although humans get tetanus shots once every 10 years, horses need boosters annually. Clostridium tetani, the bacterium that causes tetanus, thrives in soil and is also present in horses’ gastrointestinal (GI) tracts and manure. Due to the nature of equine facilities, horses are constantly exposed to C. tetani. It can contaminate wounds and produces a toxin that circulates and often proves fatal. If your horse sustains a wound or undergoes surgery more than six months after receiving his booster, he should be revaccinated.


Though it’s uncommon in horses, rabies is fatal and poses a considerable threat to public health. If your horse is vaccinated with one of the USDA-approved vaccines and exposed, he should be revaccinated right away and quarantined for 45 days for observation of clinical signs. If a horse is unvaccinated—or his rabies vaccination history is unknown—and exposed via the bite of an infected animal, he will need to be euthanized immediately or isolated under veterinary supervision for six months, per approval from public health officials.

Risk-Based Vaccines

DO ask your veterinarian about administering risk-based vaccines, recommendations for which vary by horse type and region. Vaccines protecting against diseases such as equine influenza virus (EIV), equine herpesvirus (EHV-1/4, rhinopneumonitis), equine viral arteritis (EVA), strangles, leptospirosis, Potomac horse fever, and botulism fall into the risk-based category, and your veterinarian can help you determine which ones are worth the investment.

DO consider risk-based vaccines such as those against EIV and EHV-1/4 for your performance horse if you plan to show or travel to and from equestrian venues. Performance horses spend a lot of time among large groups of horses at events. The nature of this contact creates a higher risk for contagious infectious disease spread.

“Additionally, performance horses are at risk for having variable immunity, meaning that during periods of high stress, such as intense exercise, or following long-distance transportation, they might have suppressed immunity,” says Davis.

DON’T forget to vaccinate your performance horse for EIV semiannually, especially if he’s regularly exposed to large groups of horses off the farm. Although veterinarians historically have administered these vaccines as frequently as once every quarter, the AAEP reports that all currently marketed equine influenza vaccines are likely to provide up to six months of protection.

DON’T skip botulism vaccines for your pregnant mare, especially if you live in or travel to an endemic region such as Kentucky or the mid-Atlantic. Botulism is a potentially fatal neurologic disease caused by toxins the bacterium Clostridium botulinum produces. Horses that consume round bales or fermented feeds such as haylage or silage are generally considered to be at higher risk of contracting botulism. Foals also fall into the high-risk category for another form of potentially fatal botulism called shaker foal syndrome. Foals born to unvaccinated mares can start receiving the multidose priming series at two weeks old.

DO consider risk-based vaccinations for your retired and nonperformance horses. Davis recommends building immunity for these horses, especially those living at boarding facilities, since they can still be exposed to pathogens when other horses boarded there travel to and from events.

Vaccine Administration

DON’T miss your boosters. After the initial vaccine series annual or semiannual boosters keep horses protected from disease.

“The protective immunity a horse develops after proper vaccination diminishes with time,” says Greg Schmid, DVM, a veterinarian at Columbia Equine Hospital, in Gresham, Oregon. “If enough time passes, horses’ immune systems can return to a nearly naive (nonvaccinated) state and be vulnerable to infection. Depending on the circumstances, repeating a priming series of vaccine doses, usually two or three doses, might be recommended to reestablish protective active immunity,” a process that is more expensive than simply keeping the boosters current.

While waiting to reestablish immunity, remember that your horse is at risk of contracting the diseases to which he’s become susceptible.

DON’T worry about overvaccinating. If you’re unsure about a horse’s vaccination history, talk to your veterinarian. Animal “vaccines are extensively tested and regulated by the USDA to ensure their safety, purity, potency, and effectiveness,” explains Schmid. “Although adverse reactions do occur, administering vaccines more frequently than necessary does not generally increase the risk of these reactions or diminish the immune response to vaccines.”

DO have your veterinarian administer vaccines. Although it can be tempting to save money by vaccinating your horse on your own, this DIY approach comes with several downsides. The first is a heightened risk of incorrect storage, handling, and administration.

“If a vaccine is not stored or handled properly, it could have a negative impact on the efficacy and safety,” says Schmid. “There have also been cases of improper administration techniques (e.g., injecting a vaccine too close to the neck vertebrae) that have caused serious complications.”

In addition to the increased risks to your horse, many vaccine manufacturers will not accept liability if your horse has an adverse reaction to a vaccine given by a nonveterinarian. If you own a performance horse, it is important to note that horse show management often requires proof of vaccination prior to competition, and in most cases this proof must come in the form of a health certificate. Your veterinarian might refuse to issue a health certificate if he or she did not administer the vaccines to your horse.

DO work with your veterinarian to vaccinate your pregnant mare at the appropriate times during gestation so she can transfer that immunity to her the unborn foal.

Vaccine Reactions

DO have your horse vaccinated when his heart and respiratory rates and temperature are normal. Again, adverse reactions to vaccines are uncommon, but a horse that is unwell prior to vaccination might be more likely to have a negative response. If your horse’s vitals are above normal ranges or your veterinarian recognizes clinical signs of illness when he or she arrives at the farm, it might be in the horse’s best interest to vaccinate on a different day.

DO monitor your horse for 20 to 30 minutes following vaccination. If a horse is going to react to a vaccine, it typically occurs quickly and requires immediate action from your veterinarian. Mild soreness or swelling at the vaccine site within a few hours, however, might be normal.

“The goal of administering a vaccine is to induce an immune response, both locally and systemically,” explains Davis. “The local swelling and slight warmth at the site of injection is likely a normal part of this immune response. Approximately 48 hours following vaccination, any mild swelling or stiffness should be substantially improved or completely resolved.”

If the swelling and stiffness haven’t dissipated within three days, contact your veterinarian.

Take-Home Message

Work with your vet to develop a vaccination program individualized to each horse on your property. The ultimate goal is to keep your horses healthy and protect them from preventable diseases.


Written by:

Corie Traylor is a full-time writer living in Portland, Oregon. She grew up riding horses on her family’s small farm and is currently retraining her OTTB, Bess, to be a dressage horse.

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