Childhood Diseases

08 June 2010

How do vaccines work?

Vaccines contain proteins (antigens) which come from the micro-organisms that cause the diseases they are aimed at preventing, or sometimes micro-organisms that have been altered.


Vaccines contain proteins (antigens) which come from the micro-organisms that cause the diseases they are aimed at preventing. Some vaccines contain whole micro-organisms which are killed or are altered so as not to cause disease. These then stimulate the body into producing antibodies and special white cells that will fight the infection if it appears in the future.

There are two main types of vaccine:

  • Live "attenuated" vaccines (measles, mumps, rubella, poliomyelitis). These are solutions of the micro-organisms which have been altered in such a way as to render them incapable of producing the original disease, but capable of stimulating an immune response. These are the most successful types of vaccines, generally providing life-long protection.
  • Killed vaccines (Hepatitis B, diphtheria, tetanus, whooping cough, influenza). These are solutions of dead micro-organisms which can still produce an immune response. They include inactivated bacterial toxoids (eg tetanus), whole or partial virus preparations (eg flu) and proteins made by recombinant DNA technology (eg Hep B). They require a primary course of immunisation, usually two to three injections spaced at intervals. Often booster immunisation is needed approximately every five years if immunity is to be maintained.

Reviewed by Dr Diana Hardie, Clinical Virologist employed jointly by the University of Cape Town and the National Health Laboratory Service (NHLS)
Reviewed May 2007


Read Health24’s Comments Policy

Comment on this story
Comments have been closed for this article.

Ask the Expert


Prof Eugene Weinberg worked in the Paediatrics Department of the Red Cross Children’s Hospital for many years. He is presently a paediatric allergist at the Allergy Diagnostic Unit of the UCT Lung Institute in Mowbray.

Still have a question?

Get free advice from our panel of experts

The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.

* You must accept our condition

Forum Rules