How does vaccination prevent disease?

Vaccination is designed to stimulate an immune response without causing the disease, which is the fundamental principle behind how vaccines work. When a vaccine is administered, it typically contains a harmless component of the pathogen, such as proteins, sugars, or a weakened or inactivated form of the pathogen itself. This exposure allows the immune system to recognize the pathogen as a threat and mount a defense against it.

Through this process, the immune system produces specific antibodies and activates various immune cells, such as T-cells and B-cells, which "remember" how to fight the pathogen in the future. This immunological memory provides long-lasting protection, so if the vaccinated individual is later exposed to the actual disease-causing pathogen, their immune system can respond rapidly and effectively, preventing the onset of the illness.

This mechanism emphasizes the importance of vaccination in public health, as it helps establish herd immunity and reduces the overall incidence of infectious diseases in a population.