Vaccination is an important method used in healthcare to prevent people from getting certain diseases. 

Vaccines contain  a dead or weakened (attenuated) form of a pathogen, and the immune system responds to this as if it were a real pathogen. 

1) The vaccine is given.

2) After an incubation period, white blood cells are stimulated to produce antibodies.

3) Antibodies bind to antigens on the surface of the pathogen. 

4) Special memory cells remain in the blood and speed up the immune response if the same pathogen is encountered again.