Vaccine - GCSE Biology Definition

A vaccine is a substance that helps protect people from getting infections and diseases. It works by teaching the body’s immune system to recognise and fight specific germs, such as viruses or bacteria, without causing the illness. When a person receives a vaccine, usually through an injection, their body produces memory cells that remember how to fight the germ if they are exposed to it in the future. This makes them less likely to get sick from that particular disease. Vaccines are important because they help prevent serious illness and reduce the spread of disease within communities.