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. 2021 Mar 2;9(3):207.
doi: 10.3390/vaccines9030207.

SARS-CoV-2 Infection Is Asymptomatic in Nearly Half of Adults with Robust Anti-Spike Protein Receptor-Binding Domain Antibody Response

Ourania E Tsitsilonis  1 , Dimitrios Paraskevis  2 , Evi Lianidou  3 , Evangelos Terpos  4 , Athanasios Akalestos  5 , Vassilios Pierros  6 , Evangelia Georgia Kostaki  2 , Efstathios Kastritis  4 , Paraskevi Moutsatsou  7 , Marianna Politou  8 , Andreas Scorilas  1 , Thomas Sphicopoulos  6 , Nikolaos Thomaidis  3 , Ioannis P Trougakos  1 , Athanassios Tsakris  9 , Nikolaos Voulgaris  10 , Christina C Daskalaki  1 , Zoi Evangelakou  1 , Christina Fouki  2 , Despoina D Gianniou  1 , Sentiljana Gumeni  1 , Ioannis V Kostopoulos  1 , Maria S Manola  1 , Nikolaos Orologas-Stavrou  1 , Chrysanthi Panteli  1 , Eleni-Dimitra Papanagnou  1 , Pantelis Rousakis  1 , Aimilia D Sklirou  1 , Stavroula Smilkou  3 , Dimitra Stergiopoulou  3 , Sotirios Tsiodras  11 , Meletios-Athanasios Dimopoulos  4 , Petros P Sfikakis  12
Affiliations

SARS-CoV-2 Infection Is Asymptomatic in Nearly Half of Adults with Robust Anti-Spike Protein Receptor-Binding Domain Antibody Response

Ourania E Tsitsilonis et al. Vaccines (Basel). .

Abstract

Between June and November 2020, we assessed plasma antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein in 4996 participants (aged 18-82 years, 34.5% men) from the National and Kapodistrian University of Athens. The weighted overall prevalence was 1.6% and monthly prevalence correlated with viral RNA-confirmed SARS-CoV-2 infections in Greece, in the same period. Notably, 49% of seropositive cases reported no history of SARS-CoV-2 infection-related clinical symptoms and 33% were unsuspected of their previous infection. Additionally, levels of anti-SARS-CoV-2 antibodies against the spike-protein receptor-binding domain were similar between symptomatic and asymptomatic individuals, irrespective of age and gender. Using Food and Drug Administration Emergency Use Authorization-approved assays, these results support the need for such studies on pandemic evaluation and highlight the development of robust humoral immune responses even among asymptomatic individuals. The high percentage of unsuspected/asymptomatic active cases, which may contribute to community transmission for more days than that of cases who are aware and self-isolate, underscores the necessity of measures across the population for the efficient control of the pandemic.

Keywords: SARS-CoV-2; antibodies; asymptomatic; seroepidemiology; unsuspected/asymptomatic.

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Conflict of interest statement

The authors declare no competing interests. Roche Diagnostics and NKUA-SARG had no role in the design, execution, interpretation, or writing of the study.

Figures

Figure 1
Figure 1
Seroprevalence of SARS-CoV-2 antibodies for each month of the survey and cumulative case counts per day in Greece. Blue bars show the cumulative number of SARS-CoV-2 cases recorded in Greece per day from 26 February to 4 December 2020. Red bars show the weighted seroprevalence for age and test performance estimated for the anti-SARS-CoV-2 N-protein per month (July–November) in the volunteer participants from the National and Kapodistrian University of Athens (NKUA).
Figure 2
Figure 2
Plasma levels of anti-N (left) and anti-S RBD (right) antibodies in participants from the National and Kapodistrian University of Athens (NKUA) with asymptomatic and symptomatic SARS-CoV-2 infection. Each circle represents values (cutoff index (COI) or Units (U)/mL) from a single participant. Horizontal bars indicate median values (Mann-Whitney test).
Figure 3
Figure 3
Scatter plots of SARS-CoV-2 anti-N (left) and anti-S RBD (right) antibody plasma levels of the participants from the National and Kapodistrian University of Athens (NKUA) with asymptomatic (blue symbols) and symptomatic (red symbols) SARS-CoV-2 infection stratified by gender (triangles, men; circles, women). Each symbol represents values (COI or U/mL) from a single participant (Spearman test).
See this image and copyright information in PMC

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