The MVA prototype was developed by Professor Anton Mayr in Germany through a process of 516 serial passages of the Chorioallantois Vaccina Ankara (CVA) strain of the vaccinia virus on chicken embryo fibroblasts (CEF) cells. As a consequence of these long-term passages, the resulting MVA virus lost approximately 15 percent of its genome compared to the original CVA and was essentially host cell restricted to avian cells. MVA-571 (the 571 serial passage strain) was registered in 1976 in Germany and used as a pre-vaccine before conventional smallpox vaccination and shown to be safe in more then 120,000 individuals, including high-risk subjects for smallpox vaccination.
