“…Among studies conducted in high-income settings, 15 were in European countries, 2 – 16 19 in the United States of America, 17 – 35 one in Australia, 36 three elsewhere in North America, 37 – 39 and three in Asia 40 42 There were three non-randomised interventional studies, 6 , 22 , 23 32 cohort studies, 2 – 5 , 7 – 20 , 24 , 27 – 29 , 31 – 34 , 36 – 38 , 40 – 42 three case-control studies, 21 , 25 , 30 and three cross-sectional studies 26 35 , 39 The majority of studies were conducted on children, three studies focussed specifically on neonates, 18 , 27 , 37 and three studies involved both children and adults 3 …”