  We investigate a spatially flat Friedmann-Robertson-Walker (FRW) scenario
with two interacting components, dark matter and variable vacuum energy (VVE)
densities, plus two decoupled components, one is a baryon term while the other
behaves as a radiation component. We consider a linear interaction in the
derivative dark component density. We apply the $\chi^2$ method to the
observational Hubble data for constraining the cosmological parameters and
analyze the amount of dark energy in the radiation era for the model. It turns
out that our model fulfills the severe bound of $\Omega_{x}(z\simeq
1100)<0.009$ at $2\sigma$ level, so is consistent with the recent analysis that
includes cosmic microwave background anisotropy measurements from Planck
survey, the future constraints achievable by Euclid and CMBPol experiments,
reported for the behavior of the dark energy at early times, and fulfills the
stringent bound $\Omega_{x}(z\simeq 10^{10})<0.04$ at $2\sigma$ level in the
big-bang nucleosynthesis epoch. We also examine the cosmic age problem at high
redshift associated with the old quasar APM 08279+5255 and estimate the age of
the universe today.
