When a new pathogen emerges, our bodies and healthcare systems are left vulnerable. And when this pathogen causes the outbreak of a pandemic, there's an urgent need for a vaccine to create widespread immunity with minimal loss of life. So how quickly can we develop vaccines when we need them most? Dan Kwartler describes the three phases of vaccine development. [Directed by Good Bad Habits, narrated by Jack Cutmore-Scott, music by Landon Trimble / Playdate Audio].