SARS-CoV-2 serosurvey in health care workers of the Veneto Region
Mario Plebani, Andrea Padoan, Ugo Fedeli, Elena Schievano, Elena Vecchiato, Giuseppe Lippi, Giuliana Lo Cascio, Stefano Porru, Giorgio Palù
Abstract
Objectives The ongoing outbreak of coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses formidable challenges to all health care systems. Serological assays may be used for improving disease management when appropriately applied, for investigating the antibody responses mounted against SARS-CoV-2 infection and for assessing its real prevalence. Although testing the whole population is impractical, well-designed serosurveys in selected subpopulations in specific risk groups may provide valuable information. We evaluated the prevalence of SARS-CoV-2 infection in health care workers (HCW) who underwent molecular testing with reverse transcription real-time polymerase chain reaction (rRT-PCR) in the main hospitals of the Veneto Region of Italy by measuring specific antibodies (Abs). Methods Both immunoglobulin (Ig)M and IgG antibodies against SARS-Cov-2 S-antigen and N-protein were measured using a validated chemiluminescent analytical system (CLIA) called Maglumi™ 2000 Plus (New Industries Biomedical Engineering Co., Ltd [Snibe], Shenzhen, China). Results A total of 8,285 HCW were tested. SARS-CoV-2 specific antibodies (IgM, IgG or both) were detectable in 378 cases (4.6%, 95% CI 4.1-5.0%). Seroconversion was observed in 4.4% of women vs. 5.0% of men, but this difference was not significant. Although detectable antibodies were found in all HCW who developed severe COVID-19 infection (100%), lower seropositivity was found in mild disease (83%) and the lowest prevalence (58%) was observed in asymptomatic subjects. Conclusions Seroprevalence surveys are of utmost importance for understanding the rate of population that has already developed antibodies against SARS-CoV-2. The present study defined precisely the circulation of SARS-CoV-2 in a cohort of HCW in the Veneto Region, with its prevalence (4.6%) reflecting a relatively low circulation. Symptomatic individuals or those hospitalized for medical care were 100% antibody positive, whilst Abs were only detectable in 58% of asymptomatic carriers.