Immunological memory is the ability of the immune system to remember past infections and respond more effectively to them in the future. When the body encounters a pathogen, such as a virus or bacteria, it produces specific cells called memory B cells and memory T cells. These cells remain in the body long after the infection has cleared, allowing for a quicker and stronger response if the same pathogen is encountered again. This process is crucial for long-term immunity, which is the basis for how vaccines work. Vaccines introduce a harmless part of a pathogen, prompting the immune system to create immunological memory without causing disease. As a result, if the vaccinated individual later encounters the actual pathogen, their immune system can respond rapidly and effectively, preventing illness.