  The anomaly-induced effective action is a useful tool for deriving the
contributions coming from quantum effects of massless conformal fields. It is
well-known that such corrections in the higher derivative vacuum sector of the
gravitational action provide the same exponential inflation (Starobinsky model)
as the cosmological constant term. At the same time, the presence of a
classical electromagnetic field breaks down the exponential solution. In this
paper we explore the role of the anomaly-induced term in the radiation sector
and, furthermore, derive the ``equation of state'' and the scaling laws for all
terms in the Einstein equations. As one could expect, the scaling law for the
vacuum anomaly-induced effective action is the same as for the cosmological
constant.
