For centuries, infectious diseases have spread across the world. Their deadliness has been well documented - but have they altered the path of history? Watch our latest explainer here: https://www.youtube.com/watch?v=-TkHLUnwIho | Channel 4 News

Vaccines have been instrumental in our modern view of health and healthcare. But they haven't always been around and there's been more than some misinformation on what they are and how they work. So how did we even discover vaccines in the first place? It started with a disease that had plagued humanity for so long, it seemed like it was just a natural part of living. But thanks to the work of Edward Jenner, soon smallpox would become a disease known only to history. One of two diseases that hum