They had to give some of them the real vaccine and some of them a placebo vaccine in order that they could really tell if the vaccine worked; you have to have it placebo controlled.

研究者们还须给部分孩子接种真正的疫苗,给另外一些孩子接种空白疫苗,以分辨疫苗是否真的有效,所以你必须使用安慰剂作对照

耶鲁公开课 - 生物医学工程探索课程节选

So, you didn't know at the beginning, you knew you were enrolled in the trial, they gave you a shot, you didn't know whether you were part of the real group that got the test vaccine or the placebo group that got the control; turned out that Bonnie was part of the control group.

一开始你可能不清楚全过程,你只知道你参与了一项试验,他们给你打了一针,你不知道你是属于接种了,试验疫苗的真实试验组,还是属于被注射了安慰剂的空白对照组,结果显示,邦妮属于对照组

耶鲁公开课 - 生物医学工程探索课程节选