The effects originated in dispersion with time on spreading of wave packets for the time-integrated two-flavor neutrino oscillation probabilities in vacuum are studied in the context of a field theory treatment. The neutrino flavor states are written as superpositions of neutrino mass eigenstates which are described by localized wave packets. This study is performed for the limit of nearly degenerate masses and considering an expansion of the energy until third order in the momentum. We obtain that the time-integrated neutrino oscillation probabilities are suppressed by a factor $1/L^2$ for the transversal and longitudinal dispersion regimes, where $L$ is the distance between the neutrino source and the detector.