Washington, Aug 22: A new study has revealed that mutated polio virus which resists the vaccine's protection could pose a serious threat. Scientists of the University of Bonn, together with colleagues from Gabon have reported that the polio epidemic in the Congo in 2010 caused by the mutated polio virus was especially serious. 445 people were verifiably infected, mostly young adults. The disease was fatal for 209 of them. This high mortality rate was surprising. The pathogen could also potentially have infected many people in Germany. Also important was the fact that many of those affected had apparently been vaccinated.