Facemask versus No Facemask in Preventing Viral Respiratory Infections During Hajj: A Cluster Randomised Open Label Trial

Background: This large-scale cluster-randomised controlled trial (cRCT) evaluated use of facemasks against laboratory-confirmed viral respiratory tract infections (vRTIs) and clinical respiratory infection (CRI) because previous studies have been inconclusive. Methods: An open label cRCT, conducted in Makkah compared the offer and use of 50 surgical facemasks worn over five days versus no facemasks among pilgrims. Cluster-randomisation was by accommodation tents stratified by country and gender. Tents were allocated to groups by coin-tossing. Neither participants nor recruiting investigators could be blinded to the intervention. Facemask use and respiratory symptoms were recorded daily and nasal/pharyngeal swabs were collected from symptomatic participants for detection of respiratory viruses. Clinical and laboratory data were analysed for facemask efficacy against laboratory-confirmed vRTIs and CRI. The trial is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12613001018707. Findings: From October 13 to 17 in 2013, October 2 to 6 in 2014, and September 22 to 26 in 2015, 7,687 adult participants from 318 tents were randomised to facemasks or no facemasks; 3,864 participants from 149 tents were assigned to the Facemask group and 3,823 participants from 169 tents to the Control group. In the Facemask arm, respectively 27% and 51% participants used facemasks daily and intermittently, 22% did not; in the Control arm, respectively 15% and 38% participants used facemasks daily and intermittently, 47% did not. Respiratory viruses were detected in 277 of 650 (43%) nasal/pharyngeal swabs from symptomatic pilgrims. In intention-to-treat analysis, facemask use was neither effective against laboratory-confirmed vRTIs (OR 1.35, 95% CI 0.88-2.07) nor against CRI (OR 1.1, 95% CI 0.88-1.39), not even in per-protocol analysis (OR 1.2, 95% CI 0.87-1.69; OR 1.3, 95% CI 0.99-1.83). Interpretation: Facemask use does not prevent clinical or laboratory-confirmed viral respiratory infections among Hajj pilgrims. Funding: Qatar National Research Fund (number: NPRP 6-1505-3-358). Declaration of Interest: Professor Robert Booy has received funding from Baxter, CSL, GSK, Merck, Novartis, Pfizer, Roche, Romark and Sanofi Pasteur for conducting this research, travel to conferences or consultancy work; all funding received is directed to research accounts at The Children’s Hospital at Westmead. Dr Harunor Rashid has received fees from Pfizer, Sanofi Pasteur and Novartis for consulting or serving on an advisory board. The other authors have no competing interests to declare. Ethical Approval: The trial has received approval from an Australian Human Research Ethics Committee (NSW HREC Ref: HREC/13/HNE/265), and the Joint Institutional Review Board (J-IRB) of Hamad Medical Corporation - Weill Cornell Medical College in Qatar (IRB Number: 13-00039).