<![CDATA[The COVID-19 pandemic accelerated rapid advances in vaccine development and underscored the need for platforms that can be rapidly engineered, highly effective, and adaptable to evolving pathogens. Messenger RNA (mRNA) vaccines have demonstrated exceptional efficacy and safety, establishing a significant milestone in modern vaccinology. This review aims to synthesize recent molecular engineering innovations that determine mRNA vaccine performance, focusing on nucleoside modification, spike protein prefusion stabilization, codon and untranslated region (UTR) optimization, and lipid nanoparticle (LNP) delivery systems. A literature search was conducted using PubMed and Google Scholar for studies published between 2020 and 2023, and selected publications were analyzed to identify key molecular determinants shaping vaccine function. Findings indicate that incorporation of N1-methyl-pseudouridine enhances mRNA stability, improves translational output, and reduces innate immune activation. The double-proline modification maintains the spike protein’s prefusion conformation, while codon and UTR optimization further elevate antigen expression. LNP encapsulation provides structural protection and supports efficient intracellular delivery. Collectively, these engineering strategies enhance immunogenicity, ensure favorable tolerability, and allow rapid adaptation to emerging variants. Overall, integrated molecular design and advanced delivery technologies position mRNA vaccines as a transformative platform for next-generation vaccine development and strengthened global pandemic preparedness.]]>
