Florentino 1990.

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 were eligible for inclusion in the study. Any child with clinical signs of vitamin A deficiency was excluded from the trial. Sample: 2471 children were randomised to 3 intervention groups. Mean age of children was 3.4 years, and proportion of boys in study population was 49.5%
Interventions	There were 3 study groups: 2 were supplemented with vitamin A and 1 with placebo. The first experimental group received a high dose of vitamin A (i.e. 200,000 IU), and the second experimental group received a medium dose of vitamin A (i.e. 100,000 IU). The control group received placebo only. Children were supplemented only once and were followed for 1 week.
Outcomes	Incidence of side effects within 1 week (nausea and/or vomiting, headache, diarrhoea and fever)
Notes	The study area had a high prevalence of malnutrition, and therefore vitamin A deficiency was likely to be prevalent. The study reported outcomes for the first 48 hours and within a week. We have 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 is provided. Difficult to assess sequence generation
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient details available to make a judgment
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.