Fig. 4.

Fold increase of neutralizing antibodies against live SARS-CoV-2 Delta (A) Omicron (B) variants in groups with low, medium and high baseline titers. The participants were assigned to three groups based on the GMT levels at baseline. For the Omicron variant, GMTs at D0 equal to or lower than the lower limit of quantitation (LLOQ: 20), in the range of 40–80 and over 80 were considered as low, medium and high baseline titers, respectively. For the Delta variant, GMTs at D0 equal to or lower than 80 (four times the LLOQ), in the range of 160–320 and over 320 were considered as low, medium and high baseline titers, respectively. Note: The combined data of 20 μg and 40 μg of SCTV01C were used; ∗∗∗p < 0.0001, paired statistical comparison over time.