The immune system is a 24-hour machine equipped to manage attacks from invaders to prevent or inhibit infections. It is made up of organs, tissues, and several types of cells that work together to protect the body. The immune cells must be able to determine which cells or proteins are normally in the body and which ones are foreign. Bacterial and viral cells have markers called antigens which are these foreign proteins. Each type of bacteria or virus has different antigens. Antigens are capable of inducing an immune response in the body. So, when these foreign cells or proteins enter in our body, that may cause danger, & special immune soldier cells called lymphocytes, become active. They take steps against the antigen and its owner, either by unleashing or creating antibodies to do this job. Think of it as a lock and key system. Specific antibodies remove specific antigens. The next time the antigen is identified, the body recognizes them from memory and begins to make antibodies against it. Common symptoms, like a sore throat or fever, may be present until the immune system catches up with this action. You getting a fever is one way to tell that your body is fighting invaders. That's why vaccines are useful and important. They train your immune system to create antibodies, just as it does when it’s exposed to a disease. However, because vaccines contain only killed or weakened forms of viruses or bacteria, they do not cause the disease or put you at risk of its complications. Vaccines are also called immunizations because they take advantage of our natural immune system’s ability to prevent infectious illness. When a person gets vaccinated against a disease, their risk of infection is also reduced – so they’re also less likely to transmit the virus or bacteria to others. As more people in the community get vaccinated, fewer people remain vulnerable, and there is less possibility for an infected person to pass the pathogen on to another person.