Since the development of the COVID-19 vaccines, mRNA technologies have advanced rapidly and are being widely adopted for a range of clinical applications, including vaccines, gene- and cell-therapies. Here, we describe the life cycle of an mRNA medicine, from the initial design through manufacturing, delivery, and final action, highlighting recent advances from our research and technology development. Starting with design principles, we show how our software, mRNArchitect, optimises mRNA sequences for translation efficiency and structural folding, resulting in robust and durable expression. This is complemented by a validated catalogue of sequence elements that regulate cell-specific expression. We then demonstrate how mRNA vaccines are rapidly manufactured using a novel, cell-free, isothermal reaction that enables point-of-care production for personalised mRNA medicines, such as cancer vaccines. The mRNA is then formulated into lipid nanoparticles (LNPs) to enable efficient and targeted delivery to tissues of interest. Finally, we investigate the uptake and intracellular translation of mRNA in target cells, analysing mRNA expression, processing, and presentation. Together, this provides a practical, end-to-end understanding to the development of new mRNA medicines to treat infectious disease.