I remember watching a lecture from a microbiology professor dispelling common health-related myths. I believe it was polio he was describing and how after the vaccine was developed it went from killing one in every thousand children to causing “severe reactions” (but not necessarily killing) 2 in every MILLION. There was an antivaxxer in the audience who kept repeating “but how do we know children are better off if we are vaccinating all of them now? What if they could live happier healthier lives without it??” And the prof was just like we DO know what happens, literally 1000x more children will die. Wild stuff.