Recent advances in freeze-drying technologies for mRNA vaccines against infectious diseases

Currently, the storage and transportation of mRNA vaccines typically rely on ultra-low temperature conditions. To improve their stability and extend shelf life, recent studies have been devoted to converting liquid formulations into solid forms using drying technology. Among them, freeze-drying (lyophilization) is an effective strategy that freezes samples and removes moisture through primary (sublimation) and secondary (desorption) drying stages, maximally preserving the structural integrity and biological activity of mRNA vaccines. The significant reduction in moisture content effectively inhibits the rate of hydrolysis of mRNA, which is considered the primary factor contributing to the instability of mRNA vaccines. However, the freeze-drying process itself and its accompanying stresses pose key challenges, involving many critical variables closely related to formulation composition, process parameters, and manufacturing environment. This paper systematically reviews the application of different freeze-drying technologies in mRNA vaccines and the optimization strategies of lyophilized mRNA vaccines, aiming to provide theoretical foundation and guidance for optimizing freeze-drying processes, enhancing vaccine stability and expanding their application scope.