rich1.0Ruby (npub1e8…96eju)https://yabu.me/npub1e8kmagfapqw6f6pup8aekvme3svqcryfkys9y9ck4989959m2jlsm96ejunjumphttps://yabu.mePeople knew to wash their hands since long ago and the polio vaccine came much later. Why was there a need for the vaccine to be invented?