Vision is not a 'person' per se, so therefore worthiness does not apply.
Others have suggested that it doesn't matter, that SHIELD's machinery couldn't lift it so Vision must be considered worthy, but I don't think that logic really follows, and here's why-
-The enchantment is pretty intelligent
-People using machinery could not lift it
-Stark and Rhodey using their gauntlets couldn't lift it
However
-The hammer did not make the helicarrier fall from the sky every time Thor set it down
Therefore, unless the captain of the ship (Fury) was considered Worthy, the enchantment does not extend to machinery that is being more indirectly controlled, ie ships, planes, trains, etc
Vision is a mechanical body controlled by an advanced computer program.
So he more closely adheres to the "indirect control" idea like the helicarrier.
This is why I say, he is as worthy as a table, or the coat rack in TDW
To be truly worthy, he would need a life force that the enchantment recognizes. It is possible that the infinity stone gives him that, and in which case, I would contend that it is the stone, and not any sort of inherent nobility that allows him to lift the hammer. He's no more worthy than Cap, he just already wields an artifact of even greater power than mjolnir.
The idea that Vision has a soul, which happens to be worthy, holds no scientific value because there is no such thing as a soul, scientifically speaking, only our higher cognitive functions which allow us to process concepts like morality and ethical behavior. And in the MCU, they are clearly trying to give a plausible basis to all the magical things that go on. So "souls" are out of the equation.
Basically, it boils down to 2 possibilities:
-He's inanimate, so he can lift it how the ground or any other inanimate object can
-He has the infinity stone, so can override the enchantment