If a case of polio emerged in the community, the chances that it could spread to other children or to your child were high; so, great interest in this in the early part of this century.

如果在某个社区出现一例脊髓灰质炎患儿,那么你的孩子或者更多别的孩子,被传染的几率非常高,所以 二十世纪初的科学家们,热衷于研究脊髓灰质炎

耶鲁公开课 - 生物医学工程探索课程节选

Now, the problem, or one of the challenges with clinical trials of vaccines is that you have to enroll a lot of patients into clinical trials because only a few are going to get sick in any case, only 20 out of 100,000.

现在的问题是,这也是疫苗临床试验的挑战之一,临床试验必须包括足够多的病人,毕竟只有一小部分人会被传染,十万人里面只有二十人被传染

耶鲁公开课 - 生物医学工程探索课程节选