  We present the solution of the problem of the $1/\Box, \Box \to 0,$
asymptotic terms discovered in the one-loop form factors of the gravitational
effective action. Owing to certain constraints among their coefficients, which
we establish, these terms cancel in the vacuum stress tensor and do not violate
the asymptotic flatness of the expectation value of the metric. They reappear,
however, in the Riemann tensor of this metric and stand for a new effect: a
radiation of gravitational waves induced by the vacuum stress. This coherent
radiation caused by the backreaction adds to the noncoherent radiation caused
by the pair creation in the case where the initial state provides the vacuum
stress tensor with a quadrupole moment.
