Mutant Strains of Polio Vaccine Now Cause More Paralysis Than Wild Poliohttp://www.npr.org/sections/goatsandsoda/2017/06/28/534403083/mutant-strains-of-polio-vaccine-now-cause-more-paralysis-than-wild-polio by givan • 9 years ago 3 0 9 years agoNPnpr.org