• Carlota Dobaño, Selena Alonso, Mariona Fernández de Sevilla, Marta Vidal, Alfons Jiménez, Gemma Pons Tomas, Chenjerai Jairoce, María Melé Casas, Rocío Rubio, María Hernández García, Gemma Ruiz-Olalla, Mònica Girona-Alarcón, Diana Barrios, Rebeca Santano, Robert A Mitchell, Laura Puyol, Leonie Mayer, Jordi Chi, Rodrigo MeleroNataliaNBiomolecular Screening and Protein Technologies Unit, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain., Carlo Carolis, Aleix Garcia-Miquel, Elisenda Bonet-Carne, Joana Claverol, Marta Cubells, Claudia Fortuny, Victoria Fumadó, Cristina Jou, Carmen Muñoz-Almagro, Luis Izquierdo, Quique Bassat, Eduard Gratacós, Ruth Aguilar, Juan José García-García, Gemma Moncunill, and Iolanda Jordan.
• ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Catalonia, Spain. carlota.dobano@isglobal.org.
• Bmc Med. 2021 Nov 23; 19 (1): 309.

BackgroundSurveillance tools to estimate viral transmission dynamics in young populations are essential to guide recommendations for school opening and management during viral epidemics. Ideally, sensitive techniques are required to detect low viral load exposures among asymptomatic children. We aimed to estimate SARS-CoV-2 infection rates in children and adult populations in a school-like environment during the initial COVID-19 pandemic waves using an antibody-based field-deployable and non-invasive approach.MethodsSaliva antibody conversion defined as ≥ 4-fold increase in IgM, IgA, and/or IgG levels to five SARS-CoV-2 antigens including spike and nucleocapsid constructs was evaluated in 1509 children and 396 adults by high-throughput Luminex assays in samples collected weekly in 22 summer schools and 2 pre-schools in 27 venues in Barcelona, Spain, from June 29th to July 31st, 2020.ResultsSaliva antibody conversion between two visits over a 5-week period was 3.22% (49/1518) or 2.36% if accounting for potentially cross-reactive antibodies, six times higher than the cumulative infection rate (0.53%) assessed by weekly saliva RT-PCR screening. IgG conversion was higher in adults (2.94%, 11/374) than children (1.31%, 15/1144) (p=0.035), IgG and IgA levels moderately increased with age, and antibodies were higher in females. Most antibody converters increased both IgG and IgA antibodies but some augmented either IgG or IgA, with a faster decay over time for IgA than IgG. Nucleocapsid rather than spike was the main antigen target. Anti-spike antibodies were significantly higher in individuals not reporting symptoms than symptomatic individuals, suggesting a protective role against COVID-19.ConclusionSaliva antibody profiling including three isotypes and multiplexing antigens is a useful and user-friendlier tool for screening pediatric populations to detect low viral load exposures among children, particularly while they are not vaccinated and vulnerable to highly contagious variants, and to recommend public health policies during pandemics.© 2021. The Author(s).

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