You also know that there's some vaccines that are not yet available, for diseases that we would very much like to prevent.

你们知道现在还有一些疫苗,仍没有研制出来,都是针对那些亟需预防的疾病的

耶鲁公开课 - 生物医学工程探索课程节选

And so these are situations where we would very much like to produce a vaccine, but we can't yet, and the question is 'Why? '.

我们十分想生产疫苗来解决这些问题,但我们还不行,你们会问,为什么会这样

耶鲁公开课 - 生物医学工程探索课程节选