ENCEPHALOMYELITIS - RHINOPNEUMONITIS - INFLUENZA - WEST NILE VIRUS VACCINE, EASTERN & WESTERN, KILLED VIRUS, KILLED FLAVIVIRUS CHIMERA, TETANUS TOXOID. This product has been shown to be effective for the vaccination of healthy horses 6 months of age or older against Eastern and Western encephalomyelitis viruses, EIV, EHV-1, EHV-4, tetanus, and West Nile Virus. Duration of immunity has been shown at 6 months for EIV. For more information regarding safety and efficacy data, go to productdata.aphis.usda.gov. This product has been shown to decrease virus shedding of EIV, EHV-1 and EHV-4, as well as to decrease encephalitis and viremia caused by West Nile Virus. Foals nursing immune-dams should be vaccinated when maternal antibody levels will allow active immunization.