Horses are: Eastern and Western Equine Encephalitis, Tetanus, Rabies and West Nile Virus. All other vaccines are considered "risk-based" and should be selected for a horse and booster time selected based upon the living situations, age and use of the horse. Of these vaccines, EEE, WEE and WNV should be given at least 2 weeks before the onset of mosquito and biting insect season.
Influenza and Equine Herpes Virus (Rhino) vaccinations are commonly recommended for horses that are boarded or used for competition. These vaccines may be recommended from 1-4 times a year based upon the specifics of the situation and the brand of vaccine used because they have been proven effective for 3-6 months depending on the brand.
Strangles vaccines are recommended only in specific situations due to the increased risk associated with this vaccine and the decreased efficacy of the Strangles vaccines. Strangles vaccines do NOT prevent disease but help to decrease the severity of disease and lead to adverse reactions and side effects more commonly than the core vaccines. Therefore Strangles vaccines should be given only when the situation warrants such as on breeding farms, to very young horses, situations where horses are exposed to other horses in less than ideal situations such as auctions, etc. Strangles vaccination should always be discussed with your veterinarian before being given so that the risk vs. benefit can be weighed and a choice made on vaccination. You should also be sure to discuss exactly when and how to give strangles vaccinations to minimize the risk of adverse reactions such as injection site infections.
There are many other vaccines which might be recommended based upon the exact situation such as Potomac Horse Fever, Botulism, Equine Viral Arteritis, etc. So vaccination schedules should always be layed out with the help of your local veterinarian after discussing the details of how each horse lives and works.
A really good resource for you would the www.thehorse.com
They have a wonderful series of articles on vaccination. The Horse | Vaccinations an Investment in Equine Health http://www.thehorse.com/pdf/factshee...ing-horses.pdf