Fig. 1

Patient selection. The flow of patients is depicted from screening to analysis; 274 children were screened, 102 were not eligible (non-mutually exclusive reasons for ineligibility are listed). Of the 172 provisionally eligible children, 77 could not be reached to confirm eligibility and 48 were not interested in study participation. Of the 47 randomised children, 23 were allocated to receive vitamin D and 24 to receive placebo supplementation. With one child in each group with no measurement of serum 25-hydroxyvitamin D (25OHD) after baseline, 22 and 23 children in the vitamin D and placebo groups were analysed for the main outcome. URTI, Upper respiratory tract infection