Is there a vaccination for horses against the West Nile virus ?

According to the CDC (Centers for Disease Control and Prevention), a West Nile virus vaccine was recently approved for use in horses. However, its effectiveness is currently unknown. The vaccine is only available through licensed veterinarians.

Incidentally, vaccinating your horse(s) against Eastern equine encephalitis (EEE), Western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE) will not protect them from the West Nile virus. EEE, WEE, and VEE belong to a different family of viruses than the WNV.

Sources of information:

CDC West Nile Virus FAQ

EquineWestNile.com

Hope this helps.