  A singular configuration of external static magnetic field in the form of a
pointlike vortex polarizes the vacuum of quantized massless spinor field in
2+1-dimensional space-time. This results in an analogue of the Bohm-Aharonov
effect: the chiral symmetry breaking condensate, energy density and current
emerge in the vacuum even in the case when the spatial region of nonvanishing
external field strength is excluded. The dependence of the vacuum
characteristics both on the value of the vortex flux and on the choice of the
boundary condition at the location of the vortex is determined.
