Pinnock 1988.

Study characteristics
Methods	Individually randomised study in urban area of Australia
Participants	Eligibility: children aged 0–2 years with history of bronchiolitis and nasal culture positive for RSV Excluded: children taking vitamin A; children with cystic fibrosis, cardiopulmonary difficulties, major brain dysfunctions Sample: 206 children. Mean age 58 months. 60% boys
Interventions	Experimental group: vitamin 4.2 mg per week as retinyl palmitate for 12 months Control group: placebo
Outcomes	Diarrhoea, diarrhoea‐related hospitalisation, acute respiratory infections, pneumonia, pneumonia‐related hospitalisation, mean serum vitamin A
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was achieved by randomly allocating four of eight batch numbers to vitamin A supplement and the remaining four to placebo". Quote: "the batch number code was retained by the manufacturer".
Allocation concealment (selection bias)	Low risk	Quote: "The batch number code was retained by the manufacturer. The bottles were then distributed sequentially according to batch number as children presented …". Comment: probably done.
Blinding (performance bias and detection bias) Blinding of participants	Low risk	Quote: "The placebo had an identical appearance and formulation except for the active ingredient". Comment: probably done.
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "Both investigators and parents were blind as to the treatment status of the child".
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "Both investigators and parents were blind as to the treatment status of the child … The batch number code was retained by the manufacturer".
Incomplete outcome data (attrition bias)	Low risk	Comment: complete details of those excluded and lost to follow‐up were provided.
Selective reporting (reporting bias)	High risk	Comment: outcomes mentioned in methods not reported in results.
Other bias	Low risk	Comment: study appeared free of other bias.