Figure 4.

Binding immunoglobulin (Ig) G and IgA, and neutralizing antibody titers against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are markedly increased in patients with severe coronavirus disease 2019. A–C, Scatterplots of the differences in plasma titers of binding IgG and IgA against the spike protein and the nucleoprotein (NP) of SARS-CoV-2 between intensive care unit (ICU) and non-ICU patients, regardless of time from illness onset (A) and stratified by days after symptom onset (B, C). D, Titers of neutralizing antibodies estimated by plaque reduction neutralization test (PRNT), regardless of time from illness onset and stratified by days after symptom onset. Each symbol in the scatterplots represents an individual patient, and horizontal lines represent medians. *P < .05; **P < .01; ***P < .001 (Mann-Whitney U test).