key: cord-1041718-tk3n9lak
authors: Longchamp, Alban; Longchamp, Justine; Croxatto, Antony; Greub, Gilbert; Sanchez, Bienvenido; Delaloye, Julie
title: Serum antibody response in critically ill patients with COVID-19
date: 2020-07-08
journal: Intensive Care Med
DOI: 10.1007/s00134-020-06171-7
sha: 06d22e07c3061ebcab2f246023d450588cab16f1
doc_id: 1041718
cord_uid: tk3n9lak

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already had virus-specific IgG antibodies. (Table S2 , and Fig. 1a, b) . The distribution of IgG seroconversion time from the date of ICU admission showed 2 peaks, the first one on admission, the second one about 20 days later. The median (IQR) time was 17 (1-22) days (Fig. 1b) . The distribution of IgG seroconversion time, since the onset of symptoms showed only one peak, with the median (IQR) time at 10 (7-13) days (Fig. 1c) . The proportion of patients with positive virus-specific IgG reached 96% over the follow-up period (Fig. 1a , and Table S2 ). At ICU admission, anti-N IgG levels correlated with the time from symptom onset (Fig. 1d) . No association was seen between anti-N IgG levels and age, or any of the other clinical, and laboratory data assessed (Fig. S1 ). Interestingly, two patients had no, or weak IgG seroconversion in the ICU. One had leukemia, the other one lymphoma. They died on day 4, and 38 respectively. Patients were then split into survivors (that were discharged from the ICU), and non-survivors (that died in the ICU) in order to assess if IgG seroconversion correlates with survival. IgG levels tended to be higher in patients that remained alive (mean difference ± SD, 10.3 ± 5.5, Fig. 1e ). This suggests that the antibody response correlates with virus neutralization, and functional protection [4] . Consistently, SARS-CoV-2 cycle threshold of viral RNA amplification was low during the first week of ICU stay, then gradually increased (Fig. 1f ) , simultaneously to the IgG seroconversion (Fig. 1g) . Further large-scale studies documenting the antibody responses against different SARS-CoV-2 antigens (Protein N, protein S), and viral clearance are needed to confirm our findings.

In conclusion, similarly to mild infections [4] , most patients with severe COVID-19 developed SARS-Cov-2 specific antibodies [5] . This data also suggest that the 

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