  We study the absorption spectrum of a probe field by a {\Lambda}-type
three-level system, which is coupled to a quantized control field through the
two upper energy levels. The probe field is applied to the ground and the
second excited states. When the quantized control field is in vacuum, we derive
a threshold condition to discern vacuum induced transparency (VIT) and vacuum
induced Autler- Townes splitting (ATS). We also find that the parameter change
from VIT to vacuum induced ATS is very similar to that from broken PT symmetry
to PT symmetry. Moreover, we find the photon number resolved spectrum in the
parameter regime of vacuum induced ATS when the mean photon number of the
quantized control field is changed from zero (vacuum) to a finite number.
However, there is no photon number resolved spectrum in the parameter regime of
VIT even that the quantized control field contains the finite number of
photons. Finally, we further discuss possible experimental realization.
