What happens in our body when we vaccinate? What is the difference between a live-attenuated vaccine and an inactivated vaccine. Are combination vaccines safe? Why do some vaccines protect a lifetime while others need to be refreshed? In the second part, I explain exactly how a vaccination works.

How does our immune system work and how works a vaccination?
The immune system has the mission to protect the organism from dangerous pathogens. One of the defense strategies of the immune system is the formation of so-called antibodies. Upon contact with a pathogen, the immune system forms suitable antibodies tailored to this pathogen. In addition, the immune system has so-called memory cells that remember the pathogen. In a second contact with this pathogen, the immune system is already prepared, recognizes the pathogen and can react much faster, and already has the antibodies ready as a weapon. The vaccines are based on these functions of the immune system. In vaccination, pathogens or parts of them are administered in an attenuated or killed and harmless form. They are so attenuated that they don’t cause a disease or only in a weak form, but stimulate the immune system to form memory cells and antibodies. When the real pathogen comes along, the immune system is already prepared and can combat the pathogen before it causes symptoms. With a vaccination the immune system learns. It is a kind of training for the emergency.

What is the difference between live-attenuated and inactivated vaccine?
Live-attenuated vaccines contain the pathogen still able to proliferate but attenuated that it cannot cause a disease. Inactivated vaccines contain the pathogen or parts of it in a devitalized form. Most of the vaccines are inactivated vaccines.

Why some vaccines protect a lifetime while others need to be refreshed?
As already mentioned, vaccination means to train the immune system so that later it can recognize the pathogen and react immediately. The stronger the confrontation with the pathogen is, the better and more lasting is the memory of the immune system. Live-attenuated vaccines shape the immune system just as well as a real infection. Because the attenuated vaccines are still able to proliferate after administration, the immune system has to work much more. The memory of the pathogen is more emphatic. In contrast, normally the inactivated vaccine needs more than one vaccination (2-3) before it develops a basic immunization.

Are combination vaccines safe?
Combination vaccines are vaccines against more (three or four) infectious diseases in one administration. One might think that the simultaneous vaccination with different pathogens could be too heavy for the immune system. In truth, we have to deal with a lot of more pathogens in our environment every day. A child’s immune system can do it very well. Combination vaccines are therefore preferable to single vaccines whenever available. Less picking is more pleasant for the child! The use of combination vaccines keeps also the quantity of additives as low as possible.

Are reactions to a vaccination normal?
Yes, they are! A vaccine, like any medication, is an intervention in our organism. Side effects are therefore possible and normal. They can be seen as a positive sign that the body deals with the pathogen and builds up the desired protection. Local reactions could be redness and swelling. Generalized reactions could be feeling sick, headache, muscular and articulation pain, fatigue and lightly elevated corporal temperature. However the symptoms are much lighter after vaccination than the real infection.