Vaccine

A vaccine is an antigenic preparation used to produce active immunity to a disease, in order to prevent or ameliorate the effects of infection by any natural or 'wild' strain of the organism. The term derives from vaccinia, the infectious viral agent of cowpox, which, when administered to humans, provided them protection against smallpox. The process of distributing and administrating vaccines is referred to as vaccination.

Types of vaccines

Vaccines may be living, weakened strains of viruses or bacteria which intentionally give rise to inapparent-to-trivial infections. Vaccines may also be killed or inactivated organisms or purified products derived from them.

Related Topics:
Virus - Bacteria

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There are three types of traditional vaccineshttp://www.immunecentral.com/infotemplate.cfm-1702-72-1:

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• Inactivated - these are previously virulent micro-organisms that have been killed with chemicals or heat. Examples are vaccines against flu, cholera, plague, and hepatitis A. Most such vaccines may have incomplete or short-lived immune responses and are likely to require booster shots.
• Live, attenuated - these are live micro-organisms that have been cultivated under conditions to disable their virulent properties. They typically provoke more durable immunological responses and are the prefered type for healthy adults. Examples include flu, yellow fever, measles, rubella, and mumps.
• Toxoids - these are inactivated toxic compounds from micro-organisms in cases where these (rather than the micro-organism itself) causes illness. Examples of toxoid-based vaccines include tetanus and diphtheria

The live tuberculosis vaccine is not the contagious TB strain, but a related strain called "BCG"; it is used in the United States very infrequently.

Related Topics:
Tuberculosis - Contagious - BCG

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A number of innovative vaccines are also in development and also in use:

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• Conjugate - certain bacteria have polysaccharide outer coats that are poorly immunogenic. By linking these outer coats to proteins (e.g. toxins), the immune system can be led to recognize the polysaccharide as if it were a protein antigen.
• Subunit - rather than introducing a whole inactivated or attenuated micro-organism to an immune system, a fragment of it can create an immune response
• Recombinant Vector - by combining the physiology of one micro-organism and the DNA of the other, immunity can be created against diseases that have complex infection processes
• DNA vaccination - in recent years a new type of vaccine, created from an infectious agent's DNA called DNA vaccination, has been developed. It works by insertion (and expression, triggering immune system recognition) into human or animal cells, of viral or bacterial DNA. These cells then develop immunity against an infectious agent, without the effects other parts of a weakened agent's DNA might have. As of 2003, DNA vaccination is still experimental, but shows some promising results.