To address the requirement for the request for prototype mRNA-based vaccines to counteract biological threat agents issued by the Joint Program Executive Office for Chemical, Biological, Radiological, and Nuclear Defense (JPEO-CBRND), the University of Texas, Medical Branch (UTMB), along with partners at HDT Bio Corp. and the National Institute of Allergy and Infectious Diseases (NIAID) Rocky Mountain Labs (RML), will develop and demonstrate prototype mRNA vaccines targeting Crimean-Congo hemorrhagic fever virus (CCHFV) and Nipah virus (NiV). Case fatality rates for CCHFV can be as high as 30%, and despite wide-geographic spread and continued infections of humans each year, there are no approved vaccines or antivirals for CCHFV. NiV causes febrile encephalitis and severe respiratory disease in humans with a fatality rate as high as 100% in some outbreaks. Currently, there are no vaccines licensed for the prevention of NiV disease, and one that could be deployed during outbreaks or troop deployment to endemic regions is urgently needed. The goal of the project is to design, develop, conduct non-clinical testing, manufacture, and conduct human clinical trials for the mRNA vaccines to evaluate their potential for successful licensure by the FDA. The prototype vaccines will shorten the timelines for emergency response to biological threat outbreaks and prevent/minimize the impact of biological threats, hazards, exposures, and their effects to military personnel.