Lipid adjuvants act as a fundamental element in mRNA vaccine technology by performing as diverse functional parts: augmenting immune responses, assisting genetic payload delivery to target cells, and optimizing antigen presentation. They offer various advantages, such as particle stabilization, targeted delivery, refined endosomal escape mechanisms, and self-adjuvant characteristics that amplify immune activation. The lipid adjuvant structure is crucial for both maximizing delivery accuracy and unlocking tunable immune responses, positioning lipid adjuvants as critical components of next-generation vaccines. Understanding the structural alterations of the lipid adjuvants is necessary for the rational design and synthesis of next-generation novel lipid adjuvants that elicit superior immune responses in mRNA vaccines. To magnify the potency and safety of lipid adjuvants, researchers are investigating the fundamental aspects of designing an innovative lipid that leverages biodegradable linkages. This strategy emphasizes the critical roles of numerous lipids, such as ionizable/cationic lipids, helper lipids, phospholipids, and PEGylated lipids, for enhancing the stability, targeting precision, and immunogenic efficacy of mRNA vaccine delivery. Moreover, it elucidates the structural changes of recently developed cationic/ionizable lipid adjuvants, highlighting how their structure impacts vaccine efficacy, especially linkers. By leveraging these advancements, researchers are exploring the potential for highly effective and targeted mRNA vaccine platforms, paving the way for next-generation immunization strategies.