  It is argued that close to a Coulomb interacting quantum critical point, the
interaction between two vortices in a disordered superconducting thin film
separated by a distance $r$ changes from logarithmic in the mean-field region
to $1/r$ in the region dominated by quantum critical fluctuations. This gives
support to the charge-vortex duality picture of the observed reflection
symmetry in the current-voltage characteristics on both sides of the
transition.
