Effect of Distributing Locally Produced Cloth Facemasks on COVID-19-Like Illness and All-Cause Mortality – a Cluster-Randomised Controlled Trial in Urban Guinea-Bissau

Background: Facemasks have been employed to mitigate the spread of SARS-CoV-2. The community effect of providing cloth facemasks on COVID-19 morbidity and mortality is unknown.Methods: In a cluster randomised trial in urban Bissau, Guinea-Bissau, between 20 July 2020 and 22 January 2021 trial participants (aged 10+ years) living in intervention clusters received two 2-layer cloth facemasks. All participants received information on COVID-19 prevention. Trial participants were followed through a telephone interview for COVID-19-like illness (3+ symptoms), care seeking, and mortality for 4 months. End-of-study home visits ensured full mortality information and distribution of facemasks to the control group. Proportions experiencing outcomes were compared in logistic regression models with generalised estimating equation-based correction for cluster. Facemasks use was mandated. Facemask use in public areas was assessed by direct observation.Findings: Among the 39,574 trial participants enrolled, 95% reported exposure to groups of >20 persons and 99% reported facemasks use, with no difference between trial arms. Observed use was substantially lower (~40%) with a 3% (0-6%) absolute difference between control and intervention clusters. Half of those wearing a facemask wore it correctly. Few participants reported COVID-19-like illness (<2%); proportions did not differ by trial arm: Odds Ratio (OR)=0.81 (95%CI:0.57-1.15). 177 participants reported consultations and COVID-19-like illness (OR=0.83 (0.56-1.24)); 89 persons died (OR=1.34 (0.89-2.02)).Interpretation: Trial participants were exposed to many people, but facemasks were mostly not worn or not worn correctly. Providing facemasks and messages about correct use did not substantially increase use and had limited impact on morbidity and mortality.Funding Statement: Novo Nordisk Foundation (NNF20SH0064649), Reinholdt W. Jorck Fonden (20-JP-0299), Augustinus fonden (20-1196), COWIfonden (APE/knl/A_149.14) and University of Southern Denmark.Declaration of Interests: None to declare. Ethics Approval Statement: Our trial protocol was approved by the Guinean National Ethics Committee (Comité Nacional de Ética na Saúde, reference: 79/CNES/INASA/2020).Trial Registration: clinicaltrials.gov: NCT04471766