Crimean-Congo Hemorrhagic Fever

The goal of this clinical trial is to assess the safety, tolerability and immunogenicity of three dosage levels, and a single or two-dose administration regimen, of the investigational HDT-321 product administered intra-muscularly. The main questions it aims to answer are: * Is HDT-321 safe to use * Does HDT-321 provide protection against Crimean-Congo hemorrhagic fever virus (CCHFV) Researchers will record any adverse events and test blood samples to see if HDT-321 is safe and works to protect participants against Crimean-Congo hemorrhagic fever virus (CCHFV) Participants will: * Receive 1 or 2 doses of HDT-321 * Complete a memory aid and measurements for 7 days after receiving each dose of HDT-321 * Be followed throughout the study using phone calls and clinic visits to check for and record adverse events * Provide blood samples at specific study visits

CCHF has a wide geographical distribution with cases mainly occurring in Asia, the Middle East, South-Eastern Europe and Africa. Since its emergence in 2002, Turkiye has been the epicentre of activity worldwide reporting up to more than 1000 cases annually. CCHF case management relies on the provision of optimised supportive care; therapeutic options lack a robust evidence base The UMIT-2 Trial (UMIT = 'Hope' in Turkish) will be the first large randomised controlled trial of novel therapeutics in CCHF, undertaken in multiple trial sites in Turkiye and Iraq. It uses an efficient adaptive platform design (Phase IIb), focussed on antiviral efficacy with interim monitoring to introduce new arms and allow early stopping for futility, efficacy, or safety