  A massless spinor field is quantized in the background of a singular static
magnetic vortex in 2+1-dimensional space-time. The method of self-adjoint
extensions is employed to define the most general set of physically acceptable
boundary conditions at the location of the vortex. Under these conditions, all
effects of polarization of the massless fermionic vacuum in the vortex
background are determined. Absence of anomaly is demonstrated, and patterns of
both parity and chiral symmetry breaking are discussed.
