Seroprevalence of SARS-CoV-2-specific antibodies in the town of Ariano Irpino (Avellino, Campania, Italy): a population-based study

The Italian municipality of Ariano Irpino (Avellino, Campania, Italy) was locked down by the regional authorities from March until April 2020 after several citizens tested positive for SARS coronavirus 2 (SARS-CoV-2). A serological mass screening campaign targeting the Ariano Irpino population using the Roche Cobas Elecsys anti-SARS-CoV-2 assay was organized by the Zoo-Prophylactic Institute of Southern Italy (Portici, Italy) and conducted in cooperation with the Local Health Unit (Azienda Sanitaria Locale - ASL - Avellino, Avellino, Italy), the Department of Public Health of University Federico II (Naples, Italy) and Department of Health Services of Azienda Ospedaliera dei Colli-Cotugno and Monaldi Hospital (Naples, Italy) in May 2020. A total of 13,218 asymptomatic individuals were reviewed in this analysis. A total of 738 citizens tested positive for anti-SARS-CoV-2 antibodies (398 females, 340 males). The overall prevalence in the sample was 5.6% (95% CI: 5.2-6.0). Among seropositive citizens, 101 cases tested positive on RT-PCR (0.76% of the overall population). Among citizens aged 14-18, 18-65 and >65 years, the seroprevalence was equal to 6.1 (95% CI: 4.1-8.7), 5.6 (95% CI: 5.1-6.1) and 4% (95% CI: 3.3-4.8), respectively. In the pediatric cohort (<14 years old), seroprevalence was 13% (95% CI: 10.2-16.2). A serological-based screening strategy could be a cost-effective public health intervention to tackle the COVID-19 pandemic.