Equine West Nile Vaccines
Risk of exposure and geographic distribution of West Nile virus vary
from year to year with changes in distribution of insect vectors and
reservoirs of the virus. Because of the unpredictable nature of those
factors and the effects of the disease, it is recommended that all
horses in North America be immunized against West Nile virus.
Vaccination is the primary method of reducing the risk of infection from
West Nile virus to the horse but clinical disease is not fully
prevented. Following the label instructions, primary vaccination of
previously non-vaccinated horses involves administration of 2 doses of
vaccine 3 to 6 weeks apart. In endemic areas, boosters are required or
warranted according to local conditions conducive to disease risk.
Vaccinate semi-annually or more frequently (every 4 months), depending
on risk. Annual re-vaccination is best completed in the spring, prior to
the onset of peak insect vector season.