*Article* **Prevalence of Antibodies to SARS-CoV-2 in Italian Adults and Associated Risk Factors**

**Antonio Vena 1, Marco Berruti 1,2, Andrea Adessi 3, Pietro Blumetti 4, Michele Brignole 5,6, Renato Colognato 4, Germano Gaggioli 7, Daniele Roberto Giacobbe 1, Luisa Bracci-Laudiero 8,9, Laura Magnasco 1, Alessio Signori 10, Lucia Taramasso 1, Marco Varelli 11, Nicoletta Vendola 12, Lorenzo Ball 13,14, Chiara Robba 14, Denise Battaglini 14, Iole Brunetti 14, Paolo Pelosi 13,14 and Matteo Bassetti 1,2,\***


Received: 29 June 2020; Accepted: 18 August 2020; Published: 27 August 2020

**Abstract:** We aimed to assess the prevalence of and factors associated with anti- severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) positivity in a large population of adult volunteers from five administrative departments of the Liguria and Lombardia regions. A total of 3609 individuals were included in this analysis. Participants were tested for anti-SARS-CoV-2 antibodies [Immunoglobulin G (IgG) and M (IgM) class antibodies] at three private laboratories (Istituto Diganostico Varelli, Medical Center, and Casa della Salute di Genova). Demographic data, occupational or private exposure to SARS-CoV-2-infected patients, and prior medical history consistent with SARS-CoV-2 infection were collected according to a preplanned analysis. The overall seroprevalence of anti-SARS-CoV-2 antibodies (IgG and/or IgM) was 11.0% [398/3609; confidence interval (CI) 10.0%–12.1%]. Seroprevalence was higher in female inmates than in male inmates (12.5% vs. 9.2%, respectively, *p* = 0.002), with the highest rate observed among adults aged >55 years (13.2%). A generalized estimating equations model showed that the main risk factors associated with SARS-CoV-2 seroprevalence were the following: an occupational exposure to the virus [Odd ratio (OR) = 2.36; 95% CI 1.59–3.50, *p* = 0.001], being a long-term care facility resident (OR = 4.53; 95% CI 3.19–6.45, *p* = 0.001), and reporting previous

symptoms of influenza-like illness (OR = 4.86; 95% CI 3.75–6.30, *p* = 0.001) or loss of sense of smell or taste (OR = 41.00; 95% CI 18.94–88.71, *p* = 0.001). In conclusion, we found a high prevalence (11.0%) of SARS-CoV-2 infection that is significantly associated with residing in long-term care facilities or occupational exposure to the virus. These findings warrant further investigation into SARS-CoV-2 antibody prevalence among the Italian population.

**Keywords:** SARS-CoV-2; COVID-19; antibodies; serological test
