  The electromagnetically induced transparency (EIT) phenomenon in earlier
universe is considered. We evaluated the elementary processes of the single
scattering of photon on the hydrogen atom with the purpose of their use in the
tasks of the radiation transfer theory. The additional function $f$, which
depends on external conditions, is found. This function can be considered as an
adjustment of the optical depth that leads to the necessity of modernization of
the escape probability $p_{ij}(\tau_S)\rightarrow p_{ij}(\tau_S(1+f))$. The
numerical values of $f$ for the different schemes of atom in three-level
approximation are given. It is found that the magnitude of function $f$ could
influence significantly on the formation of CMB in some partial cases.
