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Unravelling the role of the mandatory use of face covering masks for the control of SARS-CoV-2 in schools: a quasi-experimental study nested in a population-based cohort in Catalonia (Spain)
  1. Ermengol Coma1,
  2. Martí Català2,
  3. Leonardo Méndez-Boo1,
  4. Sergio Alonso3,
  5. Eduardo Hermosilla1,4,
  6. Enric Alvarez-Lacalle3,
  7. David Pino3,
  8. Manuel Medina1,
  9. Laia Asso5,
  10. Anna Gatell6,
  11. Quique Bassat7,8,9,10,11,
  12. Ariadna Mas12,
  13. Antoni Soriano-Arandes13,14,
  14. Francesc Fina Avilés1,
  15. Clara Prats3
  1. 1 Sistemes d’Informació dels Serveis d’Atenció Primària (SISAP), Institut Català de la Salut, Barcelona, Catalonia, Spain
  2. 2 Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
  3. 3 Department of Physics, Universitat Politècnica de Catalunya, Barcelona, Catalonia, Spain
  4. 4 IDIAP Jordi Gol, Barcelona, Catalonia, Spain
  5. 5 Departament de Salut, Generalitat de Catalunya, Barcelona, Catalonia, Spain
  6. 6 Equip Pediatria Territorial Alt Penedès-Garraf, Institut Català de la Salut, Barcelona, Catalonia, Spain
  7. 7 ISGlobal, Hospital Clínic—Universitat de Barcelona, Barcelona, Catalonia, Spain
  8. 8 Centro de Investigação em Saúde de Manhiça, Manhica, Maputo, Mozambique
  9. 9 Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
  10. 10 Pediatrics Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Esplugues (Barcelona), Catalonia, Spain
  11. 11 ICREA, Catalan Institution for Research and Advanced Studies, Barcelona, Catalonia, Spain
  12. 12 Direcció Assistencial d'Atenció Primària i a la Comunitat, Institut Català de la Salut, Barcelona, Catalonia, Spain
  13. 13 Paediatric Infectious Diseases and Immunodeficiencies Unit, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
  14. 14 Department of Infectious Diseases, Vall d'Hebron Research Institute, Barcelona, Catalonia, Spain
  1. Correspondence to Dr Antoni Soriano-Arandes, Paediatric Infectious Diseases and Immunodeficiencies Unit, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain; tsorianoarandes{at}


Objective To assess the effectiveness of mandatory use of face covering masks (FCMs) in schools during the first term of the 2021–2022 academic year.

Design A retrospective population-based study.

Setting Schools in Catalonia (Spain).

Population 599 314 children aged 3–11 years attending preschool (3–5 years, without FCM mandate) and primary education (6–11 years, with FCM mandate).

Study period From 13 September to 22 December 2021 (before Omicron variant).

Interventions A quasi-experimental comparison between children in the last grade of preschool (5 years old), as a control group, and children in year 1 of primary education (6 years old), as an interventional group.

Main outcome measures Incidence of SARS-CoV-2, secondary attack rates (SARs) and effective reproductive number (R*).

Results SARS-CoV-2 incidence was significantly lower in preschool than in primary education, and an increasing trend with age was observed. Six-year-old children showed higher incidence than 5 year olds (3.54% vs 3.1%; OR 1.15 (95% CI 1.08 to 1.22)) and slightly lower but not statistically significant SAR (4.36% vs 4.59%; incidence risk ratio 0.96 (95% CI 0.82 to 1.11)) and R* (0.9 vs 0.93; OR 0.96 (95% CI 0.87 to 1.09)). Results remained consistent using a regression discontinuity design and linear regression extrapolation approaches.

Conclusions We found no significant differences in SARS-CoV-2 transmission due to FCM mandates in Catalonian schools. Instead, age was the most important factor in explaining the transmission risk for children attending school.

  • COVID-19
  • epidemiology
  • paediatrics
  • child health

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Data availability statement

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  • Twitter @ErmengolComa, @LMBooster, @SergioAlonsoMun, @eduboniqueta, @kilocurie, @pino_in_bcn, @laia_asso, @GatellAnna, @tonisoriano66, @prats_clara

  • Contributors EC, SA, AS-A, FF and CP: Conceptualisation. EC, MC, LM, SA, EH, FF and CP: Methodology. EC, MC, LM, SA, EH, AS-A, FF and CP: Validation. EC, MC, LM, SA, EH, FF and CP: Formal analysis. EC, LM, EH, AM, MM, LA and FF: Resources. EC, MC, LM, SA, EH, EA-L, DP, QB, AS-A, FF and CP: Writing—original draft preparation. All authors: Visualisation. EC, SA, AS-A, FF and CP: Supervision. CP, EC: Guarantors.

  • Funding CP and SA received funding from Ministerio de Ciencia, Innovación y Universidades and FEDER, with the project PGC2018-095456-B-I00. AS-A received funding from the Generalitat of Catalunya, with the project Sentinel Schools.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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