With the current COVID-19 pandemic, the market for vaccinations is widely believed to be characterized by market failures, because individuals do not internalize the positive externalities that their vaccination decisions may confer on other individuals. Since the pioneering works by Richard Nelson and Kenneth Arrow in the early sixties, economists have developed a framework to explain the systemic underinvestment in R&D (research and development), which is an obvious cause of the current pandemic crisis. In your opinion, what are the reasons for underinvestment in vaccine R&D?