The problem with being healthy is that you completely forget what it feels like to be sick. In 2019, many people assume that the history of vaccination is recent history -- maybe a few centuries of innovation starting in the late 1700s. The truth is much more convoluted: centuries of ancient customs developing slowly into a cycle of extremes -- scientific innovation followed by fear, rejection, and sometimes, violence. In the first episode of our special series, 'Infectious,' we explore this recurring cycle and how it echoes still in 2019.