How do Live Vaccinations Work?


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There are a number of different types of vaccination used in the world today, and each of these confers its own distinct set of advantages and disadvantages. In this article we look at how one particular type of vaccination works to immunise people against potent and contagious diseases. This type of vaccine is referred to as a live attenuated vaccine, or sometimes simply as a live or attenuated vaccine. These are usually injectable vaccinations that are very good at conferring strong immunity with as little as a single dose.

What is a live vaccine?

A live vaccine is one in which a live virus or bacterium is present and used to immunise people against a particular disease. The form of the pathogen (micro-organism which causes disease) used in these vaccines is different to the wild type which actually causes the disease in that it is usually a weakened form (referred to as attenuated). For example the measles and mumps vaccines found in MMR are often grown inside chicken eggs so that the viruses are adapted to that environment and are less effective in the human body.

Mechanism of how live vaccines work

Live vaccines are actually very effective at what they do, and provide strong immunities when delivered. A great example of an effective live vaccine is the MMR vaccine which protects against measles, mumps, and rubella, and others include the yellow fever vaccine and the oral polio vaccine.

Live vaccines are so effective at what they do because they are very close to the wild type pathogen that would actually cause the disease, and yet not so much so that they pose a real through and cause sickness.

They work by effectively preparing the immune system for an encounter with a particular pathogen. Our immune system is a highly evolved and extremely sophisticated system which defends us against infection, and one of its most remarkable features is its capacity to remember specific infections once they have encountered them, and thereby defend against them more effectively upon subsequent infections.

It takes time for a body to mount its defence against a new pathogen, and in some cases that time can be ill afforded as the illness spreads. What a live vaccine does is cut short this reaction time, so that should you become exposed to a dangerous disease like polio, its effects are limited because your body responds to it quickly and efficiently, sparing you from an unpleasant and sometimes severe illness.


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