How does immunization cause diseases??


And


How do microbes cause diseases

Look, microbes don't even know we exist. They just go about their business, living, feeding, reproducing, giving off waste products. When we get in their way they can cause us trouble because either we have no immunity or there are just large numbers of them ganging up on us at once. For instance if you don't wash your hands before you eat or you touch a doorknob after someone else who is sick or you accidentally eat food that is spoiled. If you get immunized against something maybe the vaccine was weak or too old to work right or the microbe itself has mutated to develop resistance to the vaccine making it a poor fit to protect you.