Source: Kelsey Perreault
A therapy that involves injecting an augmented/altered pathogen into a person to induce active immunity; vaccines prepare a person for when they are naturally exposed to specific pathogens by stimulating them to already have the proper antibodies and memory cells in their systems.
A unique marker that has the potential to stimulate an immune response; antigens are basically the identity marker of cells for the immune system to see.
Also known as specific immunity, active immunity is carried out by T & B lymphocytes and reacts to specific antigens of cells; active immunity also produces memory cells to target the same pathogen if we are ever exposed to it again.
Not every vaccine has lifelong effects, so when antibody levels decline after a certain period of time a booster shot is given to bring the back up again.