Question

how can imunizations prevent certian diseases

Answer 1

The diseases that vaccines prevent can be dangerous, or even deadly. Vaccines reduce the risk of infection by working with the body's natural defenses to help it safely develop immunity to disease. When germs, such as bacteria or viruses, invade the body, they attack and multiply. 

Answer 2

Well, they contain weak or dead cells of the illness so your body can form an immunization against it for future issues. That's the simple answer.