Frequency of asymptomatic carriers of SARS-CoV-2 among children and adults after school reopening

Background: Children often develop an asymptomatic form of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), but it is debated if children are at higher risk than adults to be asymptomatic carriers of SARS-CoV-2, especially during the school reopening. The main aim of this study was to investigate the frequency of SARS-CoV-2 asymptomatic carriers in children and adults during the reopening of the schools in Milan, Italy. Methods: We conducted a cross-sectional study at the pediatric and adult Emergency Department (ED) of the Ca' Granda Ospedale Maggiore Policlinico (Milan) between October 1 and 31, 2020, i.e. 3 weeks after the reopening of schools. Patients admitted to the ED short stay observation and without any sign or symptom consistent with a SARS-CoV-2 were eligible. These patients underwent a nasopharyngeal swab specimen for the detection of SARS-CoV-2. The odds ratio and its 95% confidence interval (CI) was calculated to assess the risk of asymptomatically carrying the SARS-CoV-2 infection in children and adults. Results: A total of 69 (27 females, median age 8.7 years) children and 251 (107 females, median age 71 years) adults were enrolled. Pediatric and adult subjects tested positive for SARS-CoV-2 with a similar frequency (1/69 [1.4%] vs 4/251 [1.6%]). Children had an odds ratio to be a carrier of 0.91 (CI 0.02– 9.38) compared to adults. Conclusions: The frequency of asymptomatic SARS-CoV-2 carriers was similar among children and adults. Considering the emerging diffusion of new SARS-CoV-2 variants, the asymptomatic spread of SARS-CoV-2 infection among children and adults should be monitored.