Abstract: The invention provides highly sensitive, specific and efficient quantitative real-time PCR compositions, methods and assay kits to detect at least one IFN subtype and/or IFN subtype allotypic variants. Primer/probe sets complementary to the coding sequence of an IFN subtype of interest avoid spurious detection of degraded mRNA and enhances the correlation between the IFN subtype that is measured by the assays of the invention and the protein that is actually expressed. The invention also provides methods for designing primers and methods of using the compositions and assay kits. The compositions, kits, and methods of the invention may be used, for example, to monitor vaccine efficacy, autoimmune disease, chronic infections, or tumor therapy.