Figure 3. SARS-CoV-2 Anti-Spike IgG and Neutralizing Antibody Responses.

Shown are geometric mean anti-spike IgG enzyme-linked immunosorbent assay (ELISA) unit responses to recombinant severe acute respiratory syndrome coronavirus 2 (rSARS-CoV-2) protein antigens (Panel A) and wild-type SARS-CoV-2 microneutralization assay at an inhibitory concentration greater than 99% (MN IC_>99%) titer responses (Panel B) at baseline (day 0), 3 weeks after the first vaccination (day 21), and 2 weeks after the second vaccination (day 35) for the placebo group (group A), the 25-μg unadjuvanted group (group B), the 5-μg and 25-μg adjuvanted groups (groups C and D, respectively), and the 25-μg adjuvanted and placebo group (group E). Diamonds and whisker endpoints represent geometric mean titer values and 95% confidence intervals, respectively. The Covid-19 human convalescent serum panel includes specimens from PCR-confirmed Covid-19 participants, obtained from Baylor College of Medicine (29 specimens for ELISA and 32 specimens for MN IC_>99%), with geometric mean titer values according to Covid-19 severity. The severity of Covid-19 is indicated by the colors of the dots for hospitalized patients (including those in intensive care), symptomatic outpatients (with samples collected in the emergency department), and asymptomatic patients who had been exposed to Covid-19 (with samples collected during contact and exposure assessment). Mean values (in black) for human convalescent serum are depicted next to (and of same color as) the category of Covid-19 patients, with the overall mean shown above the scatter plot (in black). For each trial vaccine group, the mean at day 35 is depicted above the scatterplot.