Table 1.

Study timeline and procedures

Clinic visits	Randomisation	7±3 d	10±3 d	1 m	2 m	3.5±0.5 m	7±3 d*	10±3 d*	5 m	6 m	7±0.5 m
Blood and urine samples	✓					✓					✓
Asthma phenotype and treatment	✓					✓					✓
Sun exposure questionnaire, anthropometry	✓					✓					✓
Skin colour (Fitzpatrick scale)	✓
Atopy (serum IgE)	✓
Dietary intake (vitamin D, Calcium)	✓					✓					✓
Weighting of daily vitamin D bottles	✓					✓					✓
Dispensing and/or exchange of parent questionnaires	✓					✓					✓
Nasal swab	✓					✓
Adverse health events	✓					✓					✓
URTIs, exacerbations, medications, acute care visits or hospitalisations	✓					✓					✓
Daily vitamin D supplement compliance						✓					✓
Home visits
Urine samples			✓					✓
Blood samples†			(✓)
Telephone contacts
Adverse health events		✓		✓	✓		✓		✓	✓
URTIs, exacerbations, medications, emergency visits or hospitalisations, parental work absenteeism and expenses		✓		✓	✓		✓		✓	✓
Daily vitamin D supplement compliance		✓		✓	✓		✓		✓	✓
During each asthma flare-up or URTI
Asthma flare-up diary for young children71
Effect of a child’s asthma flare-up on parents72
Summary of cold or asthma flare-up form
Nasal swab (parent-collected)
Laboratory analyses
Urinary calcium:creatinine ratio	✓		✓			✓		✓			✓
Serum calcium, phosphorus and ALP	✓		(✓)			(✓)		(✓)			(✓)
Serum 25-hydroxyvitamin D	(✓)		(✓)			(✓)		(✓)			(✓)

(✓)refers to a specimen sampled but not routinely analysed unless specifically requested by the Site endocrinologist.

*The delay is counted since the second bolus at 3.5±0.5 months.

†In a subset of patients recruited in two institutions.

ALP, alkaline phosphatase; d, days; m, months; URTI, upper respiratory tract infection.