The multiconfiguration time-dependent Hartree (MCTDH) method is employed to calculate initial-state selected reaction probabilities for the two isotopic reactions H+H-2(D-2) with initial states v=0, j=0-3 and total angular momentum J=0. To compute the reaction probabilities, an initial wave packet is prepared and propagated in time employing the recently developed constant mean-field integrator, thus reducing the computational effort by an order of magnitude. An adiabatic correction scheme is introduced which allows the initial wave packet to be moved from the asymptotic region of the educt channel close to the interaction region. The calculations are performed on the Liu-Siegbahn-Truhlar-Horowitz (LSTH) potential surface which is expanded in products of one-dimensional functions of the Jacobian coordinates. Initial-state selected reaction probabilities are computed for total energies up to 2.5 eV utilizing a combined flux operator/complex absorbing potential approach.