Figure 4. (A) SARS-CoV-2 spike, S1, and nucleocapsid levels in plasma from children with MIS-C were quantified before treatment with steroids and/or immunoglobulin replacement therapy, through 14 days following treatment (n = 11).

Shaded regions signify the limit of detection for each specific antigen test. (B) Spike and anti–spike IgM, anti–spike IgG, and anti–spike IgA levels were measured over the course of illness of a child with MIS-C. Of note, the spike protein remained above the limit of detection for the spike antigen test at the 213-day follow-up point.