Vaccines work by stimulating the immune system to produce immune molecules such as antibodies (substances produced by the body to fight disease). If you are vaccinated and come into contact with the disease itself, the antibodies produced following vaccination will fight the germs that can cause the disease a vaccine was given to prevent.

Vaccination prompts the immune system to produce its own antibodies, as though the body has been infected with a disease, but without causing sickness. This is called "active immunity". If a vaccinated person comes into contact with the germ-causing disease itself, the immune system will recognise it and immediately produce the antibodies needed to fight it.

On administration, some vaccines may prompt the immune system to produce T and B lymphocytes. Subsequently memory T and B lymphocytes are stored in the body. If a germ that the vaccine was given against enters the body of an immunized person, the memory T and B lymphocytes are released to fight and eliminate the germ from the body, without the person getting sick.


Page created on 16 March 2015

Page last updated on 27 March 2017

References: Centers for Disease Control and Prevention (CDC)