The problem is you've got to make hundreds of millions of doses sometimes in order to have an effect on progress of the disease.

问题是有时候你不得不去制造几亿支疫苗,以便在疾病进展时发挥作用

耶鲁公开课 - 生物医学工程探索课程节选

so this is hundreds of millions of doses that were given.

数据显示已有数亿支疫苗被注射

耶鲁公开课 - 生物医学工程探索课程节选

So tens or hundreds of millions of dollars would go into a study like this by the time it was completed, money that could have been used for other things, to test whether eating a low fat diet would reduce risk for breast cancer.

数以百万计的美元,投入到这样的研究,当研究结束时,本可以用来做其他事情的钱,被用来检测是否低脂膳食,可降低患乳腺癌风险

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

So you need hundreds of millions of doses, at least, and you need a way to distribute that around the world, and you need a way to keep track of who got sick and who didn't after they got vaccinated.

至少需要上亿支的剂量,还得有办法将疫苗运送到世界各地,你还要一种方法进行跟踪,在接种疫苗之后谁得病了和谁没得病

耶鲁公开课 - 生物医学工程探索课程节选