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. 2020 Sep 3;8:e9863. doi: 10.7717/peerj.9863

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© 2020 McGregor et al.

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.

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(A) Screening IgG ELISA against RBD for pre-pandemic controls (orange), IVIG (pink squares) and PCR confirmed COVID-19 sera <7 (light blue) and 7+ days from symptom onset (royal blue). Samples boxed in grey above the cut-off (red dashed line) were titrated against the spike protein. (B) Example of the confirmatory IgG titration ELISA against Spike protein. Samples above the cut-off (dashed line) in at least two consecutive dilutions are deemed seropositive (royal blue). Isotype specific ELISA against the RBD (C) and Spike (D) for IgG (blue), IgM (green) and IgA (red) in PCR confirmed COVID-19 sera <7 and 7+ days from symptom onset. One patient showed higher IgM than IgG responses and is indicated (#). AUC, area under the curve. Illustrations created with BioRender.com.