The effect of detuning on the probe absorption spectra of a two-level system in a squeezed vacuum is investigated, with and without the presence of a classically driven field. For strong squeezing, there is a threshold depending on the squeeze parameter M, which determines the positions and widths of the absorption peaks. For large detunings, the spectra exhibit a close resemblance to Fano spectra and for small detunings there is probe gain. We show that there are marked differences in the spectra between a minimum uncertainty squeezed vacuum and a field state with the maximum classical two-photon correlations . Observation of these features would confirm the essentially quantum-mechanical nature of the squeezed vacuum.