What is a vaccine?
A vaccine is any preparation intended to produce immunity to a disease by stimulating the production of antibodies. Vaccines include, for example, suspensions of killed or attenuated microorganisms, or products or derivatives of microorganisms. The most common method of administering vaccines is by injection, but some are given by mouth or nasal spray.
Unlike traditional pharmaceuticals, vaccines are prophylactic medicines designed to prevent rather than treat disease. Essentially vaccines help reduce the risk of a disease by introducing a killed or attenuated version of the disease-causing organism to the body’s immune system. If our immune system then encounters the disease-causing germ, quick recognition allows our body to fight infection with a rapid and effective immune response. In this way, vaccines mimic the body’s natural immunity.
Vaccine types and preventable diseases
| Vaccine Types | Licensed Vaccines | |
|---|---|---|
| Live attenuated vaccines |
Consist of weakened viruses or bacteria that the immune system cannot differentiate from a stronger, naturally occurring infection and consequently mounts a strong response similar to that induced by the natural disease. | BCG, cholera (oral), influenza(intranasal), measles, mumps, polio(oral), rotavirus (oral), rubella, smallpox, typhoid (oral), varicella, yellow fever. |
| Inactivated vaccines | Contain either whole or portions of killed bacteria or viruses and require several doses, generally to ‘prime’ the immune system and then ‘boost’ the immune response to provide protection. | Hepatitis A, influenza, Japanese encephalitis, polio, Q fever, rabies, tick-borne encephalitis. |
| Toxoid vaccines | Contain toxins produced by bacteria that have been inactivated to avoid toxic effects while producing a protective immune response. | Diphtheria, tetanus. |
| Sub-unit vaccines | Consist of specific proteins purified from viruses or bacteria that are capable of generating an immune response. | Anthrax, influenza, pertussis. |
| Polysaccharide vaccines | Contain purified sugar molecules taken from the surface of bacteria that can stimulate the immune system to generate antibodies. | Meningococcal, pneumococcal,typhoid. |
| Conjugate vaccines | Contain polysaccharides joined to immunestimulating molecules to develop a more robust immune response. | Haemophilus influenzae b,meningococcal, pneumococcal,typhoid. |
| Recombinant vaccines | Consist of virus proteins or live weakened viruses or bacteria produced using recombinant genetic engineering. | Hepatitis B, human papillomavirus, rotavirus (oral, reassortant). |
Page updated: March 2011