has role immunizes recipient immunizes against pathogen Eastern equine encephalitis virus Venezuelan equine encephalitis virus Western equine encephalitis virus Equus caballus combination vaccine role combination vaccine horse vaccine Eastern Equine Encephalitis Virus vaccine VEE Virus vaccine horse encephalomyelitis EEV, VEV, and WEV combination vaccine Asiyah Yu Lin a viral vaccine against horse EEV, WEV, and VEE viral infections vaccine Oliver He Western equine encephalomyelitis virus vaccine