<p>mRNA vaccines have a number of advantages over traditional vaccines: high safety (no risk of infection, minimal possibility of integration into the genome), the ability to induce both cellular and humoral immune responses, as well as the possibility of repeated administration due to the absence of antiviral immunity. The effectiveness of Moderna and Pfizer/BioNTech products that use lipid nanoparticles for mRNA delivery have been proven, but they have disadvantages, including the need for ultra-low-temperature storage and side effects associated with lipid components of vaccines. Polymers, polypeptides, dendrimers, and other delivery systems are being investigated as alternative methods of mRNA delivery. This review analyzes the side effects of mRNA vaccines encapsulated in lipid nanoparticles and promising approaches to reducing their reactogenicity.</p>