Fig. 2: Mechanistic models of Ad26.COV2.S and prototype vaccine-induced levels of SARS-CoV-2-binding and -neutralizing antibodies correlate with basic reproductive-ratio reduction (R₀) in the lung and the nose.

a, e Sigmoid-Emax models of the correlation between the level of SARS-CoV-2-neutralizing antibodies (psVNA at four weeks after vaccination, IC₅₀, log₁₀) and fractional reduction of the virus basic reproductive ratio in lung (a) and nose (e), were constructed based on data of 81 NHP obtained in three independent experiments^{1, 3}. The data were analyzed for all Ad26-based vaccine candidates combined (black line) and Ad26.COV2.S alone (green line). In all, 95% confidence intervals are represented by dashed lines in the same color. Individual datapoints (y = 0, no reduction of R₀; y = 1, 100% reduction of R₀) are represented by open circles in the same color. b ROC curves for the sigmoid-Emax models presented in panel a. f ROC curves for the sigmoid-Emax models presented in panel e. Area under the ROC curve (AUC) represents a measure of the sensitivity and specificity of the sigmoid-Emax model. c, g Sigmoid-Emax models of the correlation between the level of S-protein-binding antibodies (S ELISA at four weeks after vaccination, EU/ml, log10) and fractional reduction of the virus basic reproductive ratio in lung (c) and nose (g), based on the dataset of all vaccine candidates combined (black line) and Ad26.COV2.S alone (green line). In all, 95% confidence intervals are represented by dashed lines in the same color. Individual datapoints (y = 0, no reduction of R₀; y = 1, 100% reduction of R₀) are represented by open circles in the same color. d ROC curves for the sigmoid Emax models presented in panel c. AUC under the ROC is indicated. h ROC curves for the sigmoid Emax models presented in panel g. AUC under the ROC is indicated. Assay LOD is indicated by a vertical line, and R₀ = 1 is indicated by a horizontal line in figure a, c, e, and g. psVNA: pseudotyped virus-neutralization assay; IC₅₀: 50% neutralization antibody titer; S-ELISA: spike protein enzyme-linked immunosorbent assay; EU/mL: ELISA units per milliliter; R₀: virus basic reproductive ratio.