“…Excluding three studies, which involved HCWs deployed at Hajj, [23][24][25] all other included studies involved Hajj pilgrims. The origin of the participants varied depending on the study, seven studies included multinational participants, while the other 18 were exclusive to participants from a single country of origin; seven out of 18 (38.9%) were from Saudi Arabia, 20,[23][24][25][26][27][28] According to study types 11 out of 25 were cohort studies, 1,2,22-24,28-33 another 11 cross-sectional studies, 21,[25][26][27][34][35][36][37][38][39][40] two trials (not necessarily RCTs) 18,20 and one case-series conducted as a qualitative study 41 (Table 1).…”