Prevalence of Asymptomatic SARS-CoV-2 Infection in the General Population of the Veneto Region: Results of a Screening Campaign with Third-Generation Rapid Antigen Tests in the Pre-Vaccine Era

Silvia Cocchio, Michele Nicoletti, Francesco Paolo De Siena, Gaia Lattavo, Patrizia Furlan, Marco Fonzo, Michele Tonon, Federico Zabeo, Francesca Russo and Vincenzo Baldo
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Silvia Cocchio: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Michele Nicoletti: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Francesco Paolo De Siena: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Gaia Lattavo: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Patrizia Furlan: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Marco Fonzo: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Michele Tonon: Regional Directorate of Prevention, Food Safety, Veterinary Public Health—Regione del Veneto, 30123 Venice, Italy
Federico Zabeo: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy
Francesca Russo: Regional Directorate of Prevention, Food Safety, Veterinary Public Health—Regione del Veneto, 30123 Venice, Italy
Vincenzo Baldo: Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padua, 35131 Padua, Italy

IJERPH, 2021, vol. 18, issue 20, 1-8

Abstract: The aim of our study was to ascertain the prevalence of SARS-CoV-2 infection in the general population during a period of moderate risk, just before Italy started to implement its vaccination campaign. A third-generation antigenic nasal swab sample was collected by a healthcare provider, and all individuals testing positive subsequently had a nasopharyngeal swab for molecular testing; the result was used to calculate the positive predictive value. The population consisted of 4467 asymptomatic adults with a mean age of 46.8 ± 16.00 years. The 62.2% tested for the first time, while 37.8% had previously undergone a mean 2.2 tests for SARS-CoV-2. With 77 of our overall sample reporting they had previously tested positive for COVID-19 and 14 found positive on our screening test, the overall estimated prevalence of the infection was 0.31%. Nine of the 14 cases were confirmed on molecular testing with a PPV of 64.3%. The mean age of the individuals testing positive was 38.1 ± 17.4. Based on the timing of symptom onset, six of the above cases were classified as false negatives, and the adjusted estimated prevalence was 0.34%. Describing levels of infection in a general population seems to be very difficult to achieve, and the universal screening proved hugely expensive particularly in a low-prevalence situation. Anyway, it is only thanks to mass screening efforts that epidemiological data have been collected. This would support the idea that routine screening may have an impact on mitigating the spread of the virus in higher-risk environments, where people come into contact more frequently, as in the workplace.

Keywords: SARS-CoV-2; COVID-19; surveillance; public health; epidemiology (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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