The invention concerns in vivo and in vitro 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 in vivo expression vectors are incorporated in live vaccines. The in vivo expression vectors are used for producing in vitro 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.
