Moderna's COVID-19 vaccine relies on mRNA – messenger ribonucleic acid – to get our cells to produce a virus-free spike protein. The vaccine delivers mRNA into the body's cells in a lipid coating, like a fat bubble. Once inside, the cell produces spike proteins similar to those on the surface of SARS-CoV-2. Our immune system recognizes those vaccine-created spike proteins as invaders and creates antibodies to block future attacks.