Plague was responsible for several epidemics, including the Black Death, which killed over 50 million people in Europe in the late medieval period and represented the greatest catastrophe in human history. Today plague still kills people in outbreaks and if left untreated, bubonic plague is fatal in 40-70% of cases, rising to 100% if it progresses to the septicaemic or pneumonic forms. In recent years the number of countries where plague is endemic increased, resulting in the World Health Organization labelling it a re-emerging disease. Coupled with the risk of future antibiotic resistant strains of Yersinia pestis arising, and its potential as an aerosol-delivered bioterrorism weapon, there is a need to develop a new vaccine which is safe and effective. Prokarium is working with the UK’s Defence Science and Technology Laboratory to make thermostable and clinically test its plague vaccine candidate which gave 100% protection in a murine study.