Vaccines mimic an actual infection by a microbial pathogen like a bacteria or virus, cause our bodies to react to it and produce combative antibodies and thus provide protection from naturally occurring infectious agents. The protection provided by a vaccine makes the individual “immunized”. A vaccine can imitate a pathogen contain an alive or dead form of the microbe or parts of the microorganism that causes the host’s body to produce specific anti-pathogen antibodies and activate T cells. Vaccines may cause mild symptoms but not a serious disease caused by the pathogen. As a result of the vaccine, the individual’s body now remembers the specific infectious pathogen, it contains specific B cells, T cells, antibodies to fight it. But after a long time, the immune system may begin to forget. A second dose of vaccine called a booster is required at that time to help the immune system remember the pathogen once again and create new pathogen-specific antibodies, lymphocytes. The right time to administer a second dose or a booster is different for different types of vaccines, boosters may be given annually or within a few weeks of the first dose. It is important to get the booster doses as it will help our immune system remember the pathogens and continue to provide us with immunity.