Just like humans, pets are vulnerable to a variety of contagious illnesses. Vaccines prepare their immune systems to defend against specific diseases by mimicking a mild exposure. This way, if they encounter the real threat later on, their bodies are ready. It’s a bit like fire drills at school—the goal isn’t panic, but preparation.
Vaccination also helps reduce the spread of disease within the animal community. In some cases, such as with rabies, this protection extends to humans as well.