Pinnock 1986.

Methods	Individually randomised study in urban area of Australia
Participants	Eligibility: children aged 1‐4 years of age in 3 general practices from Adelaide. Children with more than 15 days of cough or 3 separate episodes of respiratory illness during the preceding 3 months were eligible. Sample: 147 children were randomised to the treatment groups. Mean age was 39.3 months. 50% of participants were boys
Interventions	Vitamin A administered orally as retinyl palmitate, 1160 mcg 3 times per week for 20 weeks, versus placebo
Outcomes	Acute respiratory infections, pneumonia, mean serum vitamin A
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization of treatment was achieved by combining active and placebo bottles in a sequence, which was determined by consulting a table of random numbers, and numbering the bottles accordingly." Comment: probably done
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information to permit judgment
Blinding (performance bias and detection bias) Blinding of Participants	Low risk	Quote: "The placebo was a similarly constituted syrup omitting retinyl palmitate and labelled and bottled identically."
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "All staff connected with the study remained blind to the identity of the child's medication."
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "All staff connected with the study remained blind to the identity of the child's medication."
Incomplete outcome data (attrition bias)	Low risk	Comment: a high rate of attrition, but reasons for withdrawal given and that there were no significant changes in the distribution of major potential confounding factors between the 2 groups.
Selective reporting (reporting bias)	Unclear risk	Comment: protocol not available
Other bias	Low risk	Comment: no other apparent bias was observed.