At first the title could seem misleading, since it is hard to imagine something to be natural that is produced in a laboratory. In this case it doesn’t mean that a vaccine is a thing to be found in nature, otherwise it wouldn’t be so complicated to produce them. This statement refers to the effects of vaccines: a vaccine is a preventive tool, vaccination is only the simulation of a natural process that occurs in living organisms. Vaccines aren’t used for treating illnesses; instead through them we are able to introduce a pathogen to the immune system which in the future would be recognised by it much faster, therefore these pathogens can be eliminated in time when they get in contact with the body again. Think of vaccination as an artificial infection whose purpose is to prepare your body for the future.
Everybody knows that we have an immune system to protect us from foreign threats, such as pathogens. These pathogens include for example fungi, bacteria or viruses, and they can all cause serious problems in our body. Luckily our immune system can remember the pathogens that the body has previously encountered, that is the reason why there are illnesses we don’t have to get through twice. Vaccine research and development is built on this fact, this so-called immunological memory is what serves as the basis of immunity. When a vaccine is injected in the body, the immune system responds the same way it would if this happened naturally; resulting in immunity to that certain pathogen.
In contrast to treatments with medications, vaccination is not about receiving drugs; it’s just a way of taking a step ahead of nature. The new generation of vaccines as a result of developments avoid the use of preservatives as well. The only foreign substance in some vaccines is the adjuvant, which is used to potentiate the immune responses - but adjuvants aren’t part of all vaccines.
There’s only one question left unanswered: then what exactly is in a vaccine? The answer is not so simple unfortunately. A vaccine can be for example an inactivated / weakened version or only some parts of a pathogen. There are different types of vaccines but all the safe and effective ones share these same characteristics: the injected pathogen cannot be able to do any harm in the body, but it has to have certain properties so the immune system can recognise it the next time it appears.