  We calculate vector-vector correlation functions at two loops using partially
quenched chiral perturbation theory including finite volume effects and twisted
boundary conditions. We present expressions for the flavor neutral cases and
the flavor charged case with equal masses. Using these expressions we give an
estimate for the ratio of disconnected to connected contributions for the
strange part of the electromagnetic current. We give numerical examples for the
effects of partial quenching, finite volume and twisting and suggest the use of
different twists to check the size of finite volume effects. The main use of
this work is expected to be for lattice QCD calculations of the hadronic vacuum
polarization contribution to the muon anomalous magnetic moment.
