The paper evaluates the contribution of the electromagnetically induced transparency (EIT) phenomenon to the processes of the microwave background (CMB) formation in early universe. We found the additional function $f$ to the integrated line absorption coefficient. This makes it the necessity to upgrade the Sobolev escape probability: $p_{ij}(\tau_S)\rightarrow p_{ij}\left(\tau_S\cdot\left(1+f\right)\right)$. We calculated the magnitude of the function $f$ for different schemes of the hydrogen atom in the three-level approximation in terms of the field parameters. The electric field amplitudes are defined using the CMB distribution. We found that the contribution of $f$ can be significant in some cases.