Figure 4. Neutralizing capacity of serum from individuals with mild/asymptomatic COVID-19, not requiring hospitalization.

(A) Serum was
titrated in a live viral plaque assay to measure neutralization capacity (%
inhibition of plaque formation) expressed on the Y axis vs. serum concentration
(X-axis). Different color line/symbol represents data from a single subject
with ID# shown in key in upper right, and negative control (blue triangles).
(B) Correlation between the IC50 (Y-axis) and the spike IgG ELISA OD
values (X-axis). Each symbol represents the average of replicate data points
from a single individual in key above. r2=.567 for the best fit
trend line, log(y) = .495x + 0.991. (C) Comparison of serum neutralizing
activity, IC50 (Y-axis) of the present National Guard troops (NG)
vs. hospitalized study subjects recently published. Each symbol represents
data from a single subject’s serum titration. The mean and standard error for
the different groups of study subjects is shown.