Over the past 20 years, intensive research has been conducted on the development of therapeutic mRNA, leading to numerous discoveries that have enabled its use in therapy. The main achievements in this field include increasing mRNA stability, reducing its immunogenicity (i.e., its ability to trigger an immune response), and solving the challenge of delivering mRNA into cells-all to achieve a therapeutic effect. The aim of this study was to review the scientific literature on the use of mRNA technology in the production of vaccines. Various methods of applying mRNA technology that could potentially be introduced into clinical practice in the future are described. A detailed analysis was conducted on the approved COVID-19 vaccines developed by Pfizer/BioNTech (New York, NY, USA) and Moderna (Kirkland, QC, Canada), as their introduction marked a groundbreaking moment in the advancement of mRNA technology. This study was based on the latest scientific literature from reputable publishers and medical databases such as PubMed and ClinicalTrials. In conclusion, mRNA technology is currently experiencing rapid development, significantly driven by the ongoing COVID-19 pandemic. The application of this technology holds great potential not only for vaccines against infectious diseases but also for cancer treatment. However, further research is necessary to facilitate its broader clinical implementation.