When pathogen causes the outbreak of a pandemic, there's an urgent need for a vaccine to create widespread immunity with minimal loss of life.
The fastest vaccine developed to date has been for mumps, and that took four years. With any new disease, especially one that is proving to be as complex as COVID-19, we will have to move carefully to ensure safety. Work is moving quickly, but to show that a vaccine prevents COVID-19, we have to vaccinate a large, diverse cohort of people while the virus is actively circulating, and monitor them long term.
So how quickly can we develop vaccines when we need them most? Dan Kwartler describes the three phases of vaccine development.