“…Sixteen studies did not specify their study type, and so were categorised as observational studies [28-30, 34, 38, 40-42, 44-47, 49, 50, 52, 55] (see Table 1). Twenty studies focused on HICs (Japan [27], US [28,29,32,38,[40][41][42]44], Netherlands [30], Singapore [31], Canada [33], England [34][35][36]43], South Korea [37], Sweden [39], Italy [45,46]), seven focused on LMICs (Pakistan [47,50], South Africa [48], Brazil [49], Nigeria [51], Turkey [52], Lebanon [53]), and three studies focused on larger geographical areas including multiple countries which will be referred to as regional studies (global [56], Africa [55], South-East Asia and Western Pacific [54]), listed in Table 1. One study analysed multicentre data from a number of vaccination service providers (9 healthcare facilities across Singapore) [31], 19 studies analysed routinely collected data (eight at national-level [30,34,35,37,39,41,49,55], and 11 at regional-level within the country…”