Why do I only get some illnesses once?

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Why do I only get some illnesses once?

Perhaps the most useful part of the adaptive immune response is the ability of the immune system to remember invading germs so that when they invade again the immune response is much quicker. Usually the adaptive response will take 7-10 days to get rid of the germ and cure us of the disease but if we have already been exposed to the invading germ then our immune system can recognise and attack it within 24 hours. In this case we probably won't have any symptoms or even feel slightly ill. This is why we only seem to get some illnesses once e.g. chicken pox or measles. But it's not because we're not exposed to them again but that our immune system is much more effective at getting rid of the germs the second, third, fourth etc. time around. This memory of the immune system is also the principle behind vaccination. (See the Vaccination section for more information)

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The Complete Idiot's Guide to Dangerous Diseases & Epidemics
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Date of Posting: 10/01/2003
Date of next Review: 15/01/2005

Related Questions:
How does my body protect itself against infection?
What happens if the microbes get through the first defences (the innate response)?
What is the adaptive immune response?
Why do I get some illnesses lots of times?
Why may I need to take antimicrobials?

MeSH keywords:
Immune System; Immunity; Immunity, Natural; Immunity, Active; Immunity, Cellular; Vaccination

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