Wednesday, 14 October 2009

Types Of Vaccine And How They Are Designed To Work


Child receiving a nasal spray vaccine.

In the generic sense, the process of artificially inducing immunity, in an effort to protect against infectious disease, works by 'priming' the immune system with an 'immunogen'. Stimulating immune response, via use of an infectious agent, is known as immunisation. Vaccinations involve the administration of one or more immunogens, which can be administered in several forms.

1) Inactivated vaccine: this is a virus which has been grown in culture and then killed. Certain virus proteins are intact enough to be recognised by the immune system and to provoke a response. Since the intended benefits are not thought to last, booster shots are needed.
2) Attenuated vaccine: these contain live virus particles with very low virulence. Less virulent strains are selected in the culture process, and since the virus is still reproducing, albeit slowly, fewer booster shots are needed. There is, apparently, a slight risk of reversion to virulence.
3) Virus-like particles: contain structural proteins from the virus, but lack the means to reproduce and so are not infectious.
4) A sub-unit vaccine: this presents an antigen without introducing viral particles, whole or otherwise. One method involves isolation of a specific protein from a virus. Thought to provoke a weaker immune response than other vaccines.

ROUTES OF ADMINISTRATION

A vaccine administration may be oral, by injection or by nasal spray.

So, that is how vaccines are designed to work and how they are administered. The theory is quite simple: induce an immune response by introducing a harmless version of a dangerous infectious agent and the immune system will be primed for when the dangerous model of that agent comes along. A simple theory that sounds good, but the whole process needs a little help and I shall deal with that in the next post.

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