Covid-19 RNA vaccine, illustration. The vaccine consists of strands of mRNA (messenger ribonucleic acid) encased in a lipid nanoparticle sphere. The mRNA codes for a mutated version of the viral spike protein found on the surface of the SARS-CoV-2 coronavirus that causes Covid-19. When injected into the body the mRNA is taken up by the body's cells, which manufacture copies of the protein. The proteins stimulate an immune response, causing the body to produce antibodies against the spike protein. This means that the body is primed to attack the virus should it be encountered after vaccination, preventing disease. 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.