Transmission of SARS-CoV-2 infection among children in summer schools applying stringent control measures in Barcelona, Spain

Jordan, Iolanda; de Sevilla, Mariona Fernandez; Fumado, Victoria; Bassat, Quique; Bonet-Carne, Elisenda; Fortuny, Claudia; Garcia-Miquel, Aleix; Jou, Cristina; Adroher, Cristina; Casas, María Melé; Girona-Alarcon, Mònica; Garcia, María Hernández; Tomas, Gemma Pons; Ajanovic, Sara; Arias, Sara; Balanza, Núria; Baro, Bárbara; Millat-Martinez, Pere; Varo, Rosauro; Alonso, Sergio; Álvarez-Lacalle, Enric; López, Daniel; Claverol, Joana; Cubells, Marta; Brotons, Pedro; Codina, Anna; Cuadras, Daniel; Bruijning-Verhagen, Patricia; Faust, Saul; Munro, Alasdair; Muñoz-Almagro, Carmen; Català , Martí; Prats, Clara; Garcia-Garcia, Juan José; Gratacós, Eduard

BACKGROUND: Understanding the role of children in SARS-CoV-2 transmission is critical to guide decision-making for schools in the pandemic. We aimed to describe the transmission of SARS-CoV-2 among children and adult staff in summer schools. METHODS: During July 2020 we prospectively recruited children and adult staff attending summer schools in Barcelona who had SARS-CoV-2 infection. Primary SARS-CoV-2 infections were identified through: (1) surveillance program in 22 summer schools’ of 1905 participants, involving weekly saliva sampling for SARS-CoV-2 RT-PCR during 2-5 weeks; (2)cases identified through the Catalonian Health Surveillance System of children diagnosed with SARS-CoV-2 infection by nasopharyngeal RT-PCR. All centres followed prevention protocols: bubble groups, hand washing, facemasks and conducting activities mostly outdoors. Contacts of a primary case within the same bubble were evaluated by nasopharyngeal RT-PCR. Secondary attack rates and effective reproduction number in summer schools(R*) were calculated. RESULTS: Among the over 2000 repeatedly screened participants, 30children and 9adults were identified as primary cases. A total of 253 close contacts of these primary cases were studied (median 9 (IQR 5-10) for each primary case), among which twelve new cases (4.7%) were positive for SARS-CoV-2. The R* was 0.3, whereas the contemporary rate in the general population from the same areas in Barcelona was 1.9. CONCLUSIONS: The transmission rate of SARS-CoV-2 infection among children attending school-like facilities under strict prevention measures was lower than that reported for the general population. This suggests that under preventive measures schools are unlikely amplifiers of SARS-CoV-2 transmission and supports current recommendations for school opening.