Pilot Randomised Controlled Trial to Test Effectiveness of Facemasks in Preventing Influenza-like Illness Transmission among Australian Hajj Pilgrims in 2011

Studies to determine the effectiveness of facemasks in preventing influenza have been inconclusive, largely due to small sample size. The Hajj pilgrimage, where the incidence of influenza and other respiratory infections is high, provides an excellent opportunity to test the effectiveness of facemasks against syndromic and laboratory-confirmed infections. Hence, a pilot study was conducted among Australian pilgrims to assess the feasibility of such a large-scale trial in the coming years. At the 2011 Hajj, tents were randomised to ‘supervised mask use’ versus ‘no supervised mask use’. Pilgrims with ILI symptoms for ≤3 days were recruited as ‘cases’ and those who slept within 2 meters of them as ‘contacts’. Surgical facemasks were provided to cases and contacts in the ‘mask’ tents, but not in the ‘control’ tents. Pilgrims in both groups were given diaries to record their respiratory symptoms. Nasal or pharyngeal swabs were collected from the cases and contacts with ILI for point-of-care and nucleic acid tests. A total of 22 tents were randomised to ‘mask’ (n=12) or ‘control’ (n=10). There were 164 pilgrims recruited; 75 in ‘mask’ and 89 in ‘control’ group. Mask use compliance was 76% in the ‘mask’ group and 12% in the ‘control’ group. Based on developing syndromic ILI, less contacts became symptomatic in the ‘mask’ tents compared to the ‘control’ tents (31% versus 53%, p= 0.04). However, laboratory results did not show any difference between the two groups. This pilot study shows that a large trial to assess the effectiveness of facemasks use at Hajj is feasible.