The present invention relates to the development of viral vectors expressing different immunogens from the West Nile Encephalitis Virus (WNV) or the Dengue virus which are able to induce protective humoral and cellular immune responses against WNV or Dengue virus infections. More specifically, the present invention relates to three (3) antigens from WNV (the secreted envelope glycoprotein (E), the heterodimer glycoproteins (pre-M-E) and the NSI protein) and from Dengue virus (the secreted envelope glycoprotein (e), the heterodimer glycoproteins (pre- m-e) and the nsl protein) and their use in vaccinal, therapeutic and diagnostic applications.