How does a vaccination work?

Some vaccants do not contain any germs

Vaccines help a body's immune system prepare in advance to fight infectious illnesses and potentially deadly diseases caused by infectious agents or their by-products. Essentially, vaccines give the body a preview of a bacterium, virus, or toxin allowing it to learn in advance how to defend itself against that potential invader. If the body is ever infected by that particular pathogen after the vaccine has done its work, the body's immune system is ready to protect us because it has created "memory cells" when exposed to the vaccine. These cells can tell your immune system exactly what antibodies it needs to make for that particular pathogen and can get to work before the infection gets out of control. hope that helped thank me!