Fig. 2.

(a) FAM fluorescence amplification plots (blue) from testing 10-fold serial dilutions of the “Omicron” RNA standard, representing 15 × 10⁴ down to 15 viral RNA copies per reaction. Each dilution was tested in three replicates, to evaluate the amplification efficiency. The horizontal line indicates fluorescence baseline. RFU: relative fluorescence units; (b) the corresponding standard curve; (c) comparison of the fluorescence signals obtained by testing Alpha and Omicron strains, which are both expected to be amplified by the upstream primer. The plateau fluorescence signal for the Alpha (red) is reduced compared to the respective signal for the Omicron (blue) by over 80 % RFU.