AAEP Vaccination Guidelines

The AAEP vaccination guidelines listed on this website are a summary of evidence-based recommendations regarding the use of equine vaccines currently licensed by the United States Department of Agriculture (USDA). These guidelines are designed, reviewed and periodically updated by a multi-disciplinary task-force of equine veterinarians with collective expertise in immunology, infectious disease, internal medicine and clinical practice. The vaccination recommendations represent a compilation of published data, manufacturer guidelines and a consensus of opinion among task-force members and are to be used as a resource when deciding on an effective immunization protocol for various populations of horses. These guidelines are based on a variety of risk factors including prevalence of disease, potential consequences of that disease, vaccine efficacy and safety, and susceptibility of the individual horse given their age, immune status and life-style. There is no “one-size-fits-all” vaccination program and horse owners are encouraged to work with their veterinarian to create an effective immunization protocol that also incorporates good biosecurity measures and sound husbandry practices.

Vaccines are categorized as either “core” or “at-risk” vaccines. Core vaccines are defined as those that protect horses from diseases that are endemic (very common) to a region or have potential public health significance (e.g., rabies), may be required by law, protect against virulent (deadly) and/or highly infectious organisms. Core vaccines have clearly demonstrated a high degree of safety and efficacy and thus are considered to provide a high enough level of patient benefit and low enough level of risk to justify their use in the majority of horses regardless of where they reside or what they do for a living. The 5 core vaccines for horses are tetanus, Eastern and Western Equine Encephalomyelitis (EEE and WEE), West Nile Virus (WNV) and rabies.

Risk-based vaccines are recommended after a veterinarian-guided risk-benefit analysis has been performed. The use of risk-based vaccines may vary by region of the country, groups of horses and even between individuals within a given population. Owners and trainers are encouraged to consult with their veterinarian when assessing disease-risk and the appropriate immunization protocol for their horses and / or facility. Examples of risk-based vaccines include those for equine influenza virus (EIV), equine herpesvirus 1&4 (EHV1&4), Strangles, Potomac Horse Fever and Botulism.

The decision for which horses to vaccinate, which vaccines to use and the frequency of administration should take the following factors into consideration:

Risk of the disease to the individual and/or herd: Some diseases such as EIV or EHV1&4 are highly contagious and it is beneficial to ensure that a high percentage of the herd is properly vaccinated to limit spread of these diseases within a barn or at an event such as a show or race. Good biosecurity measures are also critical in the management of highly contagious diseases. (LINK to biosecurity measures). Other diseases such as EEE, WNV, and tetanus are not spread from horse-to-horse, but are acquired from environmental sources.

Consequences of the disease itself: Some diseases such as EEE have a high mortality rate often exceeding 90%. Rabies is not only uniformly fatal for the horse but also poses a dangerous public health hazard.

Efficacy of selected vaccines: For example, proper vaccination against tetanus or rabies offers a high degree of protection against those diseases.

Economics of immunization compared to the cost of treating the disease: While EIV is rarely fatal, there may be considerable lost income associated with missed race days due to sick horses.

Potential risk of adverse events associated with vaccination: Vaccination always carries the potential risk of a reaction. Vaccine reactions may be local and characterized by focal swelling and pain at the injection site. Other reactions may be systemic and can vary from low grade fever, malaise, loss of appetite, hives and rarely fatal anaphylaxis. All adverse events should be reported to the vaccine manufacturer. In addition, adverse events can also be reported to the Center for Veterinary Biologics. 

All vaccinations should be undertaken with realistic expectations. No vaccine is 100% effective in preventing disease. Vaccination without good management practices and biosecurity protocols will not prevent infectious disease. Onset of protection following vaccination is not immediate and may require more than one dose of vaccine and / or sufficient time for the horse to mount an optimal immune response. Individual horses will vary in their response to vaccination. The immune response to vaccination can be negatively impacted by

Extremes in age: In young foals, high levels of maternally-derived colostral antibodies may adversely affect their immune response to vaccination. Senior horses may not exhibit a robust response to vaccination due to the effect of aging on the immune system (known as immunosenescence).

Poor health will adversely affect immune response. Only health, afebrile animals should be vaccinated.

Concurrent or recent administration of immunosuppressive medications such as corticosteroids may dampen the immune response.

Stress, such as long-distance transportation or strenuous exercise, can also suppress the immune system.

Improper storage, handling or administration of the vaccine can affect the efficacy of the product and make increase the risk of an adverse event.

The AAEP vaccination guidelines can be accessed in their entirety at www.aaep.org. To optimize the efficacy of any immunization protocol, it is strongly recommended that all vaccinations be administered by or under the direct supervision of your equine veterinarian.