Vaccines work to provide immunity against diseases by stimulating the immune system. When a vaccine is administered, it introduces a harmless component of the pathogen (such as inactivated or attenuated virus or bacteria, or pieces of it like proteins) that triggers an immune response. This response includes the production of antibodies, which help the body recognize and fight the actual pathogen if encountered later. Vaccination not only protects the vaccinated individual but also contributes to herd immunity, reducing the likelihood of disease spread within populations.