Why is it difficult in some cases to produce a vaccine when we've been successful in so many others?

为什么某些疾病的疫苗很难研制,即使我们已经成功生产了很多种疫苗

耶鲁公开课 - 生物医学工程探索课程节选

Why do some individuals succeed ?" despite the unfavorable circumstances?"

为什么有些人能成功,即使成长环境恶劣“

哈佛公开课 - 幸福课课程节选