Biosafety aspects of modified vaccinia virus Ankara (MVA)-based vectors used for gene therapy or vaccination

► MVA is widely used as recombinant vector for vaccination or gene therapy. ► Main biological characteristics of MVA and MVA-based recombinant vectors are reviewed. ► The use of MVA and MVA-based vectors raises several biosafety issues. ► Main issues: MVA homogeneity, nature of the transgene, recombination and shedding. ► Recommendations are given on how to deal with these issues during risk assessment.