WHEN a bacteria or virus (pathogen) enters our body, they are seen as foreign entities. Our immune system feels threatened. They start recognizing specific structures of the pathogen. Our body starts making antibodies that will bind to these structures.
The antibody and the structure in the pathogen bind together like a key and lock. The pathogen is then destroyed. That is why antibodies are specific to certain pathogen.
Our immune system also has memory. When we are attacked by the same pathogen again, the body quickly makes the same antibodies. This time we don’t even feel sick.
Vaccines contain a harmless version of a pathogen. When we are vaccinated, our bodies will have the same response in recognizing them and producing specific antibodies. the memory from our immune system helps in providing long-term protection against the pathogen.