Inoculation is a medical process that involves introducing a small amount of a disease-causing agent, such as a virus or bacteria, into the body to stimulate the immune system. This helps the body recognize and fight off the actual disease if exposed in the future. It is a key method in preventing infectious diseases. The practice of inoculation has historical roots, with early examples seen in China and India as far back as the 10th century. Today, inoculation is commonly associated with vaccines, which are designed to protect against various illnesses, including measles, influenza, and COVID-19.