ABSTRACT
INTRODUCTION: COVID-19 pandemic is one of the most serious public health events of this century. There have been more than 670 million confirmed cases and more than 6 million deaths worldwide. From the emergence of the Alpha variant to the later rampant Omicron variant, the high transmissibility and pathogenicity of SARS-CoV-2 accelerate the research and development of effective vaccines. Against this background, mRNA vaccines stepped onto the historical stage and became an important tool for COVID-19 prevention. AREAS COVERED: This article introduces the characteristics of different mRNA vaccines in the prevention of COVID-19, including antigen selection, therapeutic mRNA design and modification, and different delivery systems of mRNA molecules. It also summarizes and discusses the mechanisms, safety, effectiveness, side effects, and limitations of current COVID-19 mRNA vaccines. EXPERT OPINION: Therapeutic mRNA molecules have plenty of advantages, including flexible design, rapid production, sufficient immune activation, safety without the risk of genome insertion in the host cells, and no viral vectors or particles involved, making them an important tool to fight diseases in the future. However, the application of COVID-19 mRNA vaccines also faces many challenges, such as storage and transportation, mass production, and nonspecific immunity.