To understand how vaccines work, we need to know how our bodies make proteins.
Proteins hold the key to both how vaccines trick our immune system, and how our immune system responds to the vaccine.

Proteins are one of the key working molecules and building blocks in all cells and perform many critical functions in our bodies. Examples include collagen, which helps keep our skin firm, haemoglobin, which carries the oxygen in our blood, insulin which regulates our blood glucose levels, and antibodies, which allow the body to fight off viruses or bacteria. Proteins are made up of chains of amino acids, and with a number of different amino acids to choose from, a bewildering variety of proteins can be made by altering the unique sequence and number of amino acids in these chains. Each protein therefore has its own recipe, and because of the sheer number of different proteins it needs to make, the body keeps a recipe book.

DNA is the recipe book for proteins in our bodies and is stored within a sealed-off section of our cells, called the nucleus. The body performs two steps to convert this recipe into a specific protein.

Step 1 is to transcribe the DNA, in other words “make a certified copy of the original”. Think of copying a page out of a recipe book instead of tearing it out. This happens inside the nucleus where, as we mentioned, the DNA is stored. This copy is called messenger RNA, or mRNA for short, as it carries a message on how to make the protein.

In step 2, the mRNA is transported out of the nucleus of the cell where the recipe is read and the protein built in a process called translation, as it involves translating one language (DNA) into another (amino acids). Once mRNA has left the nucleus of the cell, it cannot pass back in. This is one reason why mRNA vaccines cannot change your DNA.