mRNA vaccine, illustration. Messenger RNA (mRNA) vaccines are given in the upper arm muscle(1). Lipid nanoparticles (LNPs) serve as a carrier that delivers the mRNA to the cell (2, 3). Once in the cytoplasm, the mRNA instructs the cell's machinery to produce a harmless piece of the pathogen, which is displayed on the cells surface (4, 5). The immune system then recognizes the unfamiliar protein and produces antibodies against it. These antibodies are then able to fight off a real infection (6).