Facemask against viral respiratory infections among Hajj pilgrims: A challenging cluster-randomized trial

What is it about?

This randomised controlled trial tested the efficacy of facemasks in preventing acute respiratory viral infection among pilgrims who attended Hajj pilgrimage in Makkah in the years 2013 (Oct), 2014 (Oct) and 2015 (Sept). The trial compared the ‘use of (simple surgical) facemasks’ versus ‘no use of facemasks’ among participants. Randomisation to each arm was in a 1:1 ratio and was done by participants’ tents. For the intervention tents free masks were provided to each participant to be worn continuously for at least 5 days of stay at Mina. They were given diaries to record their facemask use and respiratory symptoms. Data available from questionnaires, diaries and laboratory tests were analysed to examine whether facemask use made a significant difference in reducing the frequency of laboratory-confirmed viral respiratory infection and clinical respiratory infection among trial participants. A total of 7687 adult participants from 318 tents were randomised: 3864 from 149 tents to the intervention group, and 3823 from 169 tents to the control group. Participants were aged 18 to 95 (median 34) years, with a male to female ratio of 1:1.2. In the intervention arm, respectively 954 (24.7%) and 1842 (47.7%) participants used facemasks daily and intermittently, while in the control arm, (against our advice) respectively 546 (14.3%) and 1334 (34.9%) used facemasks daily and intermittently. Overall, respiratory viruses were detected in 277 of 650 (43%) nasal/pharyngeal swabs collected from symptomatic pilgrims. Facemask use was not effective against laboratory-confirmed viral respiratory infections nor against clinical respiratory infection. We assessed this by both ‘intention-to-treat’ and ‘per-protocol’ analyses, in both scenarios facemask was not effective against respiratory viral infections.

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