How vaccination works

One of the ways our society relies on to combat viral diseases is through vaccination.  But, how does that work?

First, let’s look at viruses:

http://medicineworld.org/images/blogs/11-2006/influenza-flu-virus-230.jpg

Diagram of an influenza virus from MedicineWorld.org

There are several important things to notice:

  • The coiled things on the inside, which look like springs or slinkies, are the genetic material of the virus.  Viruses only contain half the genetic material that a ‘normal’ living cell needs, so they cannot make more (reproduce) unless they invade another cell and hijack its reproductive system.
  • The wall of the virus (lipid envelope) is made up of two layers of lipid molecules.  This wall is an incredibly good barrier, preventing material from going through it.
  • The  yellow spikes and other bits that stick outside the wall are actually proteins which are embedded in the wall of the virus.  Because the double lipid wall is such a good barrier, these proteins are the ‘channels’ through which things can move across the wall.  All cells (not just viruses) have them:  they can move water and nutrients (and waste materials) through the bi-lipid cell wall, allowing a cell to ‘eat’, ‘breathe’ and communicate.

These proteins that ‘stick outside the wall’ are very important for another reason:  each type of virus (or other infecting cell) has a slightly different types of proteins sticking out, and they are arranged in slightly different ways.  Therefore, the ‘pattern’ and ‘shape’ of these proteins has become the easiest way to identify the virus.  (Scientists can also analyze the genetic structure of a virus, but this is not something our immune system can do!  So, our bodies recognize viruses by the ‘fingerprint’ of the proteins on their surface.)

An actual electron-microscope view of a virus looks like this:

http://blog.silive.com/health/2008/10/avian-flu-virus.jpg

Image on an avian influenza virus from Health&Fitness

As you can see, the proteins stick out on the outside of the wall of the virus, and they form a very specific pattern.  This is very important, because it is precisely by the specific proteins and the pattern they form that our immune system recognizes viruses (and other ‘pathogens‘, which cause infection).

Looking at the human immune system quickly will not be so easy, because it is much more complex than a simple virus is.  Let me give it a try…

When our body is infected by an ‘antigen‘ ( a pathogen which will cause our immune system to react and generate antibodies – as opposed to a poison, etc.), our immune system springs into action.  It follows a very specific chain of steps:

  • ‘General defense’:  the ‘generic’ cells which kill all kinds of ‘invaders’ are released by the immune system in hope of containing the infection within hours, before it can spread too far thoroughout one’s body.
  • If this does not work, the next line of defense begins:  this is when the body begins to defend itself against a ‘specific antigen’.
    • the body attempts to identify the infection by looking at the ‘fingerprint’ pattern of proteins on its skin/surface/cell membrane by comparing the current infection against its ‘memory database’ of past infections the body has successfully defeated
      • if it has no record of past infection that looks ‘like’ this one, it begins to ‘figure out’ the best way to fight it
        • once it figures out the best ‘antibody’ to produce, which would be most effective in fighting this specific infection, it will begin to produce it…but, figuring it out is a process of trial-and-error, and can take quite a while
      • if it finds a ‘match’ in its ‘memory database’ between the ‘fingerprint’ of the surface proteins – types and pattern – of this infection, it begins to produce the same antibodies which worked against it the last time
    • the body produces the antibodies which fight against this specific infection:  that is, it produces the very antibodies that it produced the last time it saw this pattern, and got better as a result
    • if these antibodies are strong enough to kill the infection faster than it can reproduce AND if the infection has not reached a critical level before the body can produce this antibody in sufficient amounts to conquer it, the person will survive the illness which is the result of the infection

So, how does vaccination fit the picture?

Vaccines are made up of either weakened viruses (viruses and bacteria are the most common forms of infection, and we have antibiotics to fight bacteria (viruses are too small/primitive to be killed by antibiotics)) or viruses that are dead and ‘ground up’.

When the the body ‘receives’ the vaccine, it perceives it as any other infection.  The vaccines are engineered to provoke the body to start manufacturing antibodies and the cells which recognize the’fingerprint pattern’ of the ‘antigen’ (weakened virus, or bits of the virus wall with the ‘fingerprint pattern’ of proteins on it which the body uses to recognize an infection).  In other words, the weak virus or bits of the wall of that virus will be fought – and catalogued for future use.

The theory is that if a virus (or another antigen) enters the body in the future, and the body will recognize it and produce antibodies which ‘recognize’ it and fight it.

By ‘recognizing’ the invader, the body can begin to produce the antibodies very quickly.  While some infections take a long time to overwhelm the body, other ones – the ones called ‘virulent‘ – can make one ill very, very quickly… faster than the body can find an antibody that would work!  (During the more virulent outbreaks of ‘black death‘, it was said that people could go to sleep feeling perfectly healthy, but die of the disease before the morning…)  This speed in the body’s ability to defend itself against an invading infection can mean the difference between life and death…or, at least, between a speedy recovery and an unpleasant illness.

Therefore, the philosophy behind vaccination is to introduce a non-lethat (not dangerous) form of a really bad pathogen to a body in order to get its immune system to figure out (without the danger of being ovewhelmed by the infecting disease) how to fight that specific germ, so that the body can store this information in its ‘pathogen database’.  Then, if it ever encounters the ‘full-strength’ germ, it will be able to ‘remember’ how to fight quickly – not giving the invading infection the time to become strong by spending valuable time trying to figure out how to fight it!

This is a beautiful theory!

And, like all such theories, it does actually work in many, many cases!  Unless a person has an atypical, stressed or diseased immune system, vaccination will be very effective in providing them with protection against a potential future infection.

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One Response to “How vaccination works”

  1. Measles outbreak among vaccinated kids: how it that possible? « Xanthippa's Chamberpot Says:

    [...] Vaccination is an important weapon in our arsenal of weapons against infectious diseases, as I have written about before. [...]


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