Vaccines basically prevent us from experiencing the difficult illness we were supposed to have at our first encounter with the bacteria or virus that is assaulting our body. Vaccines teach our immune system to remember the threatening pathogen so that when we get infected we won’t suffer from any illness at all, or possibly just mild symptoms. These vaccines are also called “active vaccines”, and they give our immune system a long-term memory that is useful for the following years. The vaccines are made of the pathogen in their weaker or attenuated form, or inactivated form (killed), or just parts of the pathogens that are enough for the recognition of our immune system.