Disclosed is an immunogenic composition comprising one or more strains of killed or inactivated West Nile Virus or any antigen thereof, wherein said West Nile Virus is a North American Dominant West Nile Strain or Isolate, and wherein the North American Dominant West Nile Strain or Isolate has at least one nucleotide change resulting in an amino acid change from the reference strain NY99, wherein the nucleotide change results in an amino acid change from valine to alanine at position 159 in the critical envelope protein.
