This vaccine is a long-established and effective means of reducing incidence of Eastern & Western Equine Encephalitis. It a “core” vaccines, recommended for EVERY equine, by the American Association of Equine Practitioners (AAEP).

The encephalitis vaccine is given annually as an intramuscular injection prior to mosquito season, and is commonly combined with Tetanus and West Nile vaccines. For unvaccinated horses, primary vaccination needs to be followed by a booster in 3-6 weeks. Where mosquitos are active year-round, your vet may recommend vaccination twice a year. Pregnant mares be vaccinated 4-6 weeks before foaling. As with the other core vaccines, a series of vaccinations are given to foals beginning at 4-6 months of age. When this starts may depend on the mare's vaccination status.

VEE (Venezuelan Equine Encephalitis) is an exotic disease and is generally far less likely to be a problem depending on where your horses are located and their risk.

In common with most vaccines, the active part of encephalitis vaccines is created from part of the virus that has been chemically modified to stimulate an immune response without creating disease. When this product is injected into the muscle, the viral part is recognized by immune cells, which create antibodies to that part, over weeks. If the virus later gains access to the blood, the antibodies bind to that part of the virus and destroy it before it can produce signs of disease.

There are several types of this vaccine available that rely on different vaccine technologies. Talk to your vet about which vaccine is appropriate for your horse. I recommend that your vet vaccinate your horse because they can ensure that the vaccine is handled and administered properly, and address any complications. If your vet administers the vaccine and your horse contracts the virus, some pharmaceutical companies will pay for at least part of the veterinary treatment required.