A temporary messenger with good news
The principle of vaccination is already more than 200 years old. It is based on the ingestion of a weakened form of a disease germ, to which our body's immune system responds. If someone then comes into contact with the weakened or actual micro-organism again, the immune system quickly recognizes the culprit and cleans it up.
Nowadays there are different types of vaccines. The first vaccines that are approved and available have a slightly different effect than the classic vaccine. They are so-called mRNA vaccines. This requires a few sentences of explanation about cell biology. All our human cells have a cell nucleus containing our genetic heritage, the DNA. The DNA cannot leave the cell nucleus. With our DNA we make all the building blocks of our body. For a large part these building blocks are proteins in all shapes and sizes. In order to make proteins there exist a kind of little messengers in the form of a temporary copy. These are the mRNAs. These mRNAs can leave the cell nucleus. In the cell nucleus a copy is made of the DNA for the required building block. Outside the cell nucleus, the protein factories of the cell then make the correct protein.
The effect of the vaccine is based on exactly these steps in the cell. However, we now receive copies of a virus particle, in this case from the coronavirus SARS-CoV-e. Our own cells make virus proteins from it, and our own immune system recognizes those proteins as the SARS-CoV-2 virus and produces antibodies. With this vaccine we actually put our own inner biological machine to work.
Would you like to know more? Take a look here at nucleus, or at the about vaccines.