Florentino 1990.

Study characteristics
Methods	Individually randomised trial conducted in the municipalities of Pililla and Binangonan in the province of Rizal, Philippines
Participants	Eligibility: children aged 1–6 years Excluded: any child with clinical signs of VAD Sample: 2471 children. Mean age 3.4 years. 49.5% boys
Interventions	3 intervention groups Experimental group I: single high‐dose vitamin A (200,000 IU) Experimental group II: single medium‐dose vitamin A (100,000 IU) Control group: placebo Follow‐up: 1 week.
Outcomes	Incidence of side effects within 1 week (nausea or vomiting (or both), headache, diarrhoea and fever)
Notes	The study area had a high prevalence of malnutrition, and therefore VAD was likely to be prevalent. The study reported outcomes for the first 48 hours and within 1 week. We pooled the data for the first week.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "By use of a double‐blind study design, children were randomly assigned to three treatment groups". Comment: no qualifying information on what 'randomly assigned' means. Difficult to assess sequence generation.
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient details available to make a judgement.
Blinding (performance bias and detection bias) Blinding of participants	Low risk	Quote: "Neither the researchers and field workers nor the subjects knew the contents of the preparations; the code was kept confidential by Hoffman La Roche until after the analysis of the results was completed".
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "Neither the researchers and field workers nor the subjects knew the contents of the preparations; the code was kept confidential by Hoffman La Roche until after the analysis of the results was completed". Comment: blinding adequate and performance bias unlikely to have influenced results.
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "Neither the researchers and field workers nor the subjects knew the contents of the preparations; the code was kept confidential by Hoffman La Roche until after the analysis of the results was completed".
Incomplete outcome data (attrition bias)	Low risk	Comment: complete details of those excluded and lost to follow‐up were provided. Only 76 children lost; differences slight between groups.
Selective reporting (reporting bias)	Low risk	Comment: though not explicitly stated, all reported measured outcomes have data reported in results with sufficient clarity and explanation.
Other bias	Low risk	Comment: no other apparent bias was noted.