The present invention provides an attenuated virus, which is derived from Modified Vaccinia Ankara virus and which is characterized by the loss of its capability to reproductively replicate in human cell lines. It further describes recombinant viruses derived from this virus and the use of the virus or its recombinants as medicament or vaccine. Additionally, a method for inducing an immune response even in immuno-compromised patients, patients with pre-existing immunity to the vaccine virus or patients undergoing antiviral therapies is provided.
