  We consider an analogue of the Aharonov-Bohm effect in quantum field theory:
the fermionic vacuum attains nontrivial quantum numbers in the background of a
magnetic vortex even in the case when the spatial region of nonvanishing
external field strength is excluded. The dependence of the vacuum quantum
numbers on the value of the vortex flux and the choice of the condition on the
boundary of the excluded region is determined.
