SARS-CoV-2 serology in 4000 health care and administrative staff across seven sites in Lombardy, Italy

• Published in: Scientific reports Vol. 11; no. 1; pp. 12312 - 14
• Main Authors: Sandri, Maria Teresa, Azzolini, Elena, Torri, Valter, Carloni, Sara, Pozzi, Chiara, Salvatici, Michela, Tedeschi, Michele, Castoldi, Massimo, Mantovani, Alberto, Rescigno, Maria
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.06.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/250/2152; 692/53; Anosmia; Antibody response; Coronaviruses; COVID-19; Fever; Geographical distribution; Health care; Humanities and Social Sciences; Immunoglobulin G; Medical research; multidisciplinary; Occupational exposure; Olfaction disorders; Plasma levels; Science; Science (multidisciplinary); Serology; Severe acute respiratory syndrome coronavirus 2; Sex differences; Spatial variations; Taste disorders; Italy; Lombardy Italy
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-91773-4

Lombardy is the Italian region most affected by COVID-19. We tested the presence of plasma anti-SARS-CoV-2 IgG antibodies in 3985 employees across 7 healthcare facilities in areas of Lombardy with different exposure to the SARS-CoV-2 epidemic. Subjects filled a questionnaire to self-report on COVID-19 symptoms, comorbidities, smoking, regular or remote working, and the exposure to COVID-infected individuals. We show that the number of individuals exposed to the virus depended on the geographical location of the facility, ranging between 3 and 43%, consistent with the spatial variation of COVID-19 incidence in Lombardy, and correlated with family interactions. We observed a higher prevalence of females than males positive for IgG, however the level of antibodies was similar, suggesting a comparable magnitude of the anti-spike antibody response. IgG positivity among smokers was lower (7.4% vs 13.5%) although without difference in IgG plasma levels. We observed 11.9% of IgG positive asymptomatic individuals and another 23.1% with one or two symptoms. Interestingly, among the IgG positive population, 81.2% of subjects with anosmia/dysgeusia and fever were SARS-CoV-2 infected, indicating that these symptoms are strongly associated to COVID-19. In conclusion, the frequency of IgG positivity and SARS-CoV-2 infection is dependent on the geographical exposure to the virus and primarily to family rather than hospital exposure.