There's no company that's making smallpox vaccine anymore because there's no reason to make smallpox vaccine, because nobody would buy it, right?

没有公司还生产天花疫苗,因为没有人购买天花疫苗,因此早就没有理由继续生产它了,对吧

耶鲁公开课 - 生物医学工程探索课程节选