  We use a covariant formalism that is capable of describing the electric and
magnetic versions of the Aharonov-Bohm effect, as well as the Aharonov-Casher
effect, through local interactions of charges and currents with the quantum
electromagnetic field. By considering that only local interactions of a quantum
particle with the quantum field can affect its behavior, we show that the
magnetic Aharonov-Bohm effect must be present even if the solenoid generating
the magnetic field is shielded by a perfect conductor, as experimentally
demonstrated.
