The railroad company planned to buy the machine if it worked as well as the salesman said.

VOA: special.2009.02.21

Basically, injecting it into some test subjects, making sure that they didn't get diseased from it and looking at antibody responses to see if it worked and it did.

他们把疫苗接种到测试对象体内,确定接种者不会感染疾病,同时观察抗体的应答反应,了解疫苗是否有效

耶鲁公开课 - 生物医学工程探索课程节选

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