How vaccines work
Your immune system
Your immune system is made up of a specialized network of organs, cells, and tissues that all work together to help protect you against disease. When a disease-causing germ (for example, a virus or bacteria) enters your body, your immune system:
- Recognizes the germ as being foreign (not belonging in the body).
- Responds by making special proteins (called antibodies) that help destroy the germ. Most of the time, your immune system can’t act fast enough to stop the germ from making you sick. But by destroying the germ, it can usually help you get well again.
- Remembers the germ that made you sick and how to destroy it. That way, if you are ever exposed to the same disease germ in the future, your immune system can quickly destroy it before it has a chance to make you sick. This protection is called immunity.
Vaccines and your immune system
Vaccines give you immunity to a disease without you getting sick first. They are made using killed or weakened versions of the disease-causing germ or parts of the germ (called antigens). For some vaccines, genetic engineering is used to make the antigens used in the vaccine. It’s much safer to get a vaccine than to get the disease it prevents.
When you get a vaccine, your immune system responds to the vaccine the same way it would to the real germ. It:
- Recognizes the germ in the vaccine as being foreign.
- Responds by making antibodies to the germ in the vaccine, just as it would for the real germ.
- Remembers the germ and how to destroy it. That way, if you are ever exposed to the disease-causing germ in the future, your immune system will be able to quickly destroy it before it has a chance to make you sick. This is how you get immunity from vaccines.
How Vaccines Work
Video courtesy of Health Canada. All contents may not be reproduced without permission and are copyright of Her Majesty the Queen in Right of Canada, Represented by the Minister of Health, 2012.