The 4th paragraph in the Nobel Prize press release suggests that it's because mRNA based vaccines are easier to scale up and mass produce in response to a pande

The 4th paragraph in the Nobel Prize press release suggests that it's because mRNA based vaccines are easier to scale up and mass produce in response to a pandemic: "Producing whole virus-, protein- and vector-based vaccines requires large-scale cell culture. This resource-intensive process limits the possibilities for rapid vaccine production in response to outbreaks and pandemics."