The disease that would ultimately become known AIDS was first diagnosed in June 1981. At that time, researchers had not yet determined what caused it, and by the time most patients presented with symptoms, they had only months to live. After four decades of effort by the global research community, the development of promising experimental HIV vaccines has now finally come true. We have interviewed Dr. Paolo Lusso, Chief of the Viral Pathogenesis Section at the National Institute of Allergy and Infectious Diseases, to discuss his research in developing and testing promising HIV vaccines. In this episode, Dr. Lusso explains why it took so long to develop a vaccine with the potential to defeat this “master of disguise and transformation”, words he uses to refer to HIV. Listen to this episode to learn more about the immune system, the process of developing a vaccine, and the challenges scientists had to face to stop the most invisible of all viruses.