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Originally Posted by pip08456
Is there any vaccine in existance that actually stops anyone being infected? Surely all a vaccine does is prepare the immune system to recognise and fight an infection quicker than the immune system starting from scratch.
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Not really, no as whatever infectious agent has to be in you for your immune system to act on it so you are to some extent 'infected'. A race is then on between the infectious agent multiplying and the immune system stamping it down.
Vaccines vary a lot in how much they stimulate the immune system. It does depend on how 'foreign' the disease is. A 'good' disease is one that can escape the immune system by either disguising the parts which the immune system recognises - see HIV or changing rapidly - see influenza.
You can help a bit by adding other agents which also stimulate the immune system. These are called adjuvants. When you hear about aluminium in vaccines, that is aluminium hydroxide powder which makes your immune system go crazy. It can also help by administering the vaccine through the same route as the disease (see Flumist flu vaccine and Polio vaccines) but that is really hard to do so they mostly get injected.