The invention concerns <；i>；in vivo<；/i>； and <；i>；in vitro<；/i>； expression vectors comprising a polynucleotide coding for the structural protein E of the Nile fever virus or the WN virus, optionally associated with a polynucleotide coding for the pre-membrane protein prM and/or for the membrane protein M, in particular in the form coding for prM-M-E. Said <；i>；in vivo<；/i>； expression vectors are incorporated in live vaccines. The <；i>；in vivo<；/i>； expression vectors are used for producing <；i>；in vitro<；/i>； proteins which can then be used in subunit vaccines. The invention also concerns multivalent vaccines comprising a vaccine constituent against the WN virus and a vaccine constituent against another pathogen. The invention is particular designed for horses, dogs, cats, cattle, pigs and birds.
