Certain cells in your blood make what are called ‘antibodies’, molecules which are designed to attack specific germs and viruses. These attach to the invaders in your bloodstream and prevent them from invading other cells. Each virus or bacterium has an individual shape, and the antibodies are designed to fit exactly to that shape.

This is all done by your white blood cells. You have two types called B cells and T cells. The B cells manufacture the antibodies while the T cells have two functions. The ‘helper’ T cells help the B cells to make the antibodies while the ‘killer’ T cells kill any cells which have been invaded by the viruses or bacteria, and prevent them from reproducing. . How vaccines work to stimulate this action is to mislead the white cells into believing that your body has been infected.

Viruses cannot reproduce by themselves: they have to use the host’s cells for this. If the T cells continually kill off any invaded cells, the invaders themselves must eventually be killed off by the antibodies If the virus or bacterium is strong and reproduce too quickly, the host can be overcome before it can produce enough antibodies to kill them off. The pus which occurs during an infection is the mix of dead white blood cells and bacteria/virus cells destroyed by them.

Vaccines produce the same memory effect without the patient having to suffer the disease. The organisms that cause the disease are either killed or weakened, then introduced into your body. The strength is calculated to be just enough to enable your white cells to manufacture the antibodies. This is how vaccines work to give you protection against future infection without actually making you ill. The strength of the vaccine is designed to allow this. The dead vaccine can also work, but less efficiently, and the effect is not generally as long lasting.

Vaccinations do not affect your ability to fight off other infections you have not been immunized against; in fact a 2002 German study indicated that you are likely to suffer fewer infections in general if you have had your quota of vaccinations. It is unknown exactly how vaccines work to achieve this, but it is believed that vaccination strengthens the immune system generally, and strengthens the body against other ‘secondary’ infections.

However, how vaccines work to give you immunity to the disease vaccinated against is basically by fooling or stimulating your body into producing antibodies, and the memory of their structure should the same bacteria or viruses appear again.