Disclosed is the use of an attenuated pestivirus for the preparation of a modified live vaccine for the prophylaxis and/or treatment of pestivirus infections, wherein at least the last c-terminal Cysteine-residue of the Ems glycoprotein of said attenuated pestivirus is deleted or substituted by non-Cys amino acid residue and wherein said deletion or substitution of the last c-terminal Cysteine-residue of the Ems glycoprotein results in a lack of homodimer formation of the Ems glycoprotein and leads to an attenuated pestivirus.
