Actually it is speculative assumption and conjecture based on the impression of presumed fact as determined by those who are questioning the premise.
Just because an experiment creates a repeatable result 100 times in a temporal matrix does not mean it is forever, or is even stable.
It is a group of singular events with congruent outcomes..
As the "science" of vaccines seems to change with the definition.
So we can rename a pile of dog excrement a vaccine push it into a persons body and when it does not prevent or stop the disease we can still call it a vaccine and sell it for billions of dollars to use for the expansion of a murderous monarchal plot to subjugate the populous of the world.