Vaccines teach the immune system by mimicking an infection. When a person receives an injection of a vaccine, they are exposed to a killed or weakened version of the pathogen that will not make them sick. Once the body recognizes that it is a foreign pathogen that needs to be attacked, our immune system produces leukocytes or macrophages. Once the macrophage has engulfed the pathogen, the antigens that were on the pathogen are now saved for the macrophage to use so that our lymphocytes, or T cells and B cells, can recognize them and reproduce to combat the pathogen. Defensive T cells, also called helper T cells, release chemical signals that direct the activity of other cells in the immune system. B lymphocytes make and secrete antibodies. Antibodies secreted by B cells are present throughout the human body and attack microbes that have not yet infected any cells but are floating in the blood or in the spaces between cells. When antibodies build up on the surface of a pathogen, it becomes incapable of functioning. And when T cells and antibodies begin to kill the pathogen faster than it can reproduce, the immune system has finally taken control and gradually the virus disappears from the body. And finally, once the pathogen is eliminated, some B and T cells will turn into memory cells that will reactivate and remember that particular pathogen in the future if the individual is exposed to it and then attack it (National Institutes of Heath, 2011).Types of VaccinationsThere are many types of vaccines available today. When people think of vaccines, the majority think of chickenpox, flu and others, but that's not what we're talking about today. The first type of vaccine is made from vi...... middle of paper ......hold is mandatory. Attenuated vaccines cannot be safely injected into people with compromised immune systems (i.e.…HIV). Basically, this means that these patients have weakened immune systems and struggle to cope with infections that a healthy person would barely register (UKhealth). Almost all vaccines have negative effects on people. The most common harmful consequence is redness and pain. Other negative side effects include allergic reactions, illnesses, and even nerve damage. It is rare for people to die from vaccines. As noted, there are many advantages and disadvantages to the use of vaccines. Ultimately, the benefits conferred by the use of this particular class of vaccination are great enough that health authorities around the world are resorting to live vaccination to protect the population against a multitude of different and dangerous diseases (UKhealth)