The Pfizer-BioNTech and Moderna COVID-19 vaccines are the first authorized vaccines in history to use mRNA technology. The pandemic might've set the stage for their debut, but mRNA vaccines have been in the works for more than 30 years. Host Maddie Sofia chats with Dr. Margaret Liu, a physician and board chair of the International Society for Vaccines, about the history and science behind these groundbreaking vaccines. We'll also ask, what we can expect from mRNA vaccines in the future?Have a question for us? Send a note to shortwave@npr.org — we'd love to hear it.