Editor’s Note: This is Chapter 1 of Understanding Equine Preventive Medicine by author and veterinarian Bradford G. Bentz, VMD. 

Vaccination plays a major part of a preventive medicine program, but many programs for individual horses and even for large stables are often based on incomplete understanding of the principles of vaccination and the particular needs of the animals for which the program is designed. For these reasons it is important to have realistic expectation based on a sound understanding of what particular vaccination programs provide.

Vaccination minimizes the risk of infection but does not prevent disease in all circumstances. To be effective, a primary series of vaccinations with a complete booster series must be administered prior to exposure to an infectious disease.

It should be noted, though, that not all horses respond similarly to a vaccine, and the duration of immunity against a particular infectious agent can vary.  A herd approach to vaccination rather than an individual approach should be taken to control disease. This is extremely important in any barn in which diseases can be directly transmitted among horses.  The time required to produce effective immunity from vaccination using a federally licensed vaccine is usually about two to three weeks after the primary series is completed, and one or more weeks after the routine booster is administered