When is data "practice-changing"? How many Covid-19 vaccines do we need? And what does it mean when the FDA asks for more time? With the world's largest cancer conference just concluded, we explain the most important data presented at the meeting, including a blockbuster clinical trial that promises to change the treatment of advanced breast cancer. We also discuss an FDA controversy in the making, a pair of new Covid-19 vaccines, and the frustrating process of finding new treatments for depression.