Around the world, at least 53 COVID-19 vaccines are currently undergoing clinical trials. Four of the largest and most promising have reached the final Phase III stage. UC San Diego is a testing site for three of the big four: Moderna, AstraZeneca and Janssen/Johnson & Johnson. In this episode, we speak with Susan Little, MD, principal investigator for two COVID-19 clinical trials in San Diego that are focused on finding a vaccine for SARS-CoV-2. Dr. Little discusses the science behind vaccines, how they will work to address the current pandemic, and when a potential COVID-19 vaccine will be ready.