The naturalistic fallacy is similar to the appeal to nature, where the conclusion expresses what ought to be, based only on actually what is more natural. Those who use this logical fallacy infer how the world ought to be from the way it is or was in the past.
The naturalistic fallacy is very common and most people never see the problem with these kind of assertions due to accepted social and moral norms. This bypasses reason and we fail to ask why something that is, ought to be that way.
Vaccinations ought to be considered dangerous, because natural immunity is how all children were protected against diseases in the past.