I don't know about 'for a long time' but for a certain time frame this is true[0]. However we are talking about there being 21 cases of this occurring compared

I don't know about 'for a long time' but for a certain time frame this is true[0]. However we are talking about there being 21 cases of this occurring compared to pre-eradication infection levels in the 100's of thousands per year. So whilst your statement is sort of true, it is willfully misleading. [0]https://www.npr.org/sections/goatsandsoda/2017/06/28/534403083/mutant-strains-of-polio-vaccine-now-cause-more-paralysis-than-wild-polio https://www.npr.org/sections/goatsandsoda/2017/06/28/5344030...