mRNA in lipid nanoparticles, conceptual illustration. Close-up of molecules of mRNA (messenger ribonucleic acid, yellow) encapsulated in lipid nanoparticles as utilised in RNA vaccines. These nanoparticles consist of a double membrane containing multiple different types of lipids, such as phospholipids, cholesterol, and PEGylated lipids. When injected into humans, the RNA will be taken up and read by the body's cells, causing them to produce copies of viral proteins. The viral proteins will provoke an immune response, priming the body against infection with the actual virus. The first RNA vaccine approved for human use, developed against the SARS-CoV-2 coronavirus by Pfizer/BioNTech, was approved in the UK on 2nd December 2020.