mRNA vaccines operate by delivering genetic instructions that host cells translate into viral proteins, a mechanism that shifted vaccine development from whole-virus approaches to antigen-encoding nucleic acids. Katalin Karikó of the University of Pennsylvania and Drew Weissman of the University of Pennsylvania demonstrated that nucleoside-modified messenger RNA increases protein production while limiting excessive innate sensing, enabling effective antigen expression in human cells. Public health agencies including the Centers for Disease Control and Prevention and the World Health Organization report that this approach contributed to marked reductions in severe disease and hospitalizations where deployment was extensive.
Mechanism of antigen expression and presentation
Lipid nanoparticle formulations transport mRNA into muscle and antigen-presenting cells, where cellular ribosomes translate the sequence into the encoded spike protein. The translated protein is processed for presentation on major histocompatibility complex molecules, engaging CD8 cytotoxic T lymphocytes through MHC class I and CD4 helper T lymphocytes through MHC class II. Akiko Iwasaki of Yale University and other immunologists have described how the balance between innate sensing and efficient translation shapes the quality of initial T cell priming, a critical determinant of downstream memory formation documented by national research institutes such as the National Institutes of Health.
Development of durable B and T cell memory
Germinal center activity in draining lymph nodes drives somatic hypermutation and selection of high-affinity B cell clones, producing memory B cells and long-lived plasma cells that home to the bone marrow. Justin S. Turner and Ali Ellebedy at Washington University in St. Louis reported persistent germinal center responses following mRNA immunization, and Ellebedy’s group characterized antigen-specific bone marrow plasma cells that underpin sustained antibody production. Rafi Ahmed of Emory University provides foundational work on T cell memory differentiation that frames interpretation of vaccine-induced CD8 and CD4 memory pools. These coordinated B and T cell processes explain durable protection against severe outcomes while also accounting for waning antibody levels and variable neutralization of emerging viral variants.
The technological and territorial implications are notable: BioNTech in Mainz Germany and Moderna in Cambridge Massachusetts translated basic immunology into scalable manufacturing, enabling rapid global distribution and localized vaccination campaigns. Regulatory agencies and academic teams continue to monitor immune memory through serology, cellular assays, and bone marrow studies, informing iterative updates to vaccine strategies without altering the underlying principle that mRNA platforms instruct the immune system to build long-term adaptive memory.
