The science is called immunology and to help explain this a few terms need explaining.

The Bad Guys

• Antigen – this is a bad guy dervied from infections that can potentially damage us.
• In general they are bits of proteins, and they have unique individual shapes.
• Toxins – these are chemicals usually produced by an organism that destroys tissue.
• They are usually produced by bacteria.

The Good Guys

Antibodies – These are bit of proteins produced by immune cells called B cells.  They bind to antigens rendering them harmless.

Immune cells – Basically the most important are B cells and T cells.  The T cells help destrol bacteria and viruses and mop up antigens that have been attached by antibodies.  The B cells produce antibodies.

There are many other parts of the immune system.  Some cells (pictured) mop up ‘debris’ and some have a specific role in recognising antigens.  These cells release chemicals such as cytokines, complement, leukotrienes which are involved in communication between the parts of the immune system.

 What happens when an infection occurs?

Infections are caused by viruses, bacteria, parasites and fungi.  They enter the body, and can survive, feed and divide inside us.  During this process tissue is damaged.  The body will recognise the foreign material (antigens) and start instigating a defense strategy against the infection.  This can take some days and involves grabbing the antigens and finding the antibody that will ‘match it’.

This process happens constantly, usually without us being aware.  However if the infection is particularly aggressive, serious damage can occur before the infection is eliminated.  Particular organisms are notorious for resulting in life threatening illnesses.  This is where vaccination come in.

What happens if you are vaccinated.

Vaccination involves getting hold of harmless parts of the invading organism, for example a part of a bacteria’s capsule, and injecting it so the body will recognise and set up antibodies.  So if someone comes across the fully formed bacteria, the body already has primed B cells that can immediately go into action producing antibodies.  The idea is to stomp on the organism before tissue damage occurs.

So using chicken pox and as example if you ‘catch’ the chicken pox then the virus will enter the body, and there will be several days before adequate antibodies and T cells are produced to eliminate the virus.  Meanwhile the virus is rapidly dividing and causing all sorts of symptoms, such as vesicular rash, fever and occasionally life threatening complications.  You see the virus needs to be detected, analysed, and run past many possible antibodies and cells until a ‘match’ is found.  This ‘matched’ antibody is then mass produced by dividing B cells.  So this can take quite a while.  If someone is vaccinated this process has already occurred.  So when the real virus turns up, the prepared memory B cells quickly whip into action producing lots of virus killing antibodies, which will eliminate the virus before it can cause tissue damage.

one of the biggest barriers to vaccination is not understanding how it works.  Immunology is incredibly complex and is an astonishing system that has evolved over the centuries to enable us to eliminate potential disease causing organisms.  Vaccination is a way of setting up the immune system to quickly swing into gear when we come across a disease causing organism.