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
S) → p
S · (1 + f)). 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.