Van Agtmaal 1988.

Methods	Individually randomised, non‐placebo trial conducted in Thailand
Participants	Eligibility: no exclusion criteria were described Sample: study included 30 children in which 14 were in vitamin A group and 21 in control group. Participants had a mean age of 3.1 years
Interventions	Children in experimental group received a single dose vitamin A in a dose of 200,000 IU. Study participants were followed for 4 months
Outcomes	Mean vitamin A serum levels
Notes	Children were recruited from 3 rural day care centres
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "After selection, 14 children were randomly supplemented with a single, oral dose of vitamin A (110 mg retinyl palmitate, 200,000 IU),according to WHO recommendations (9), and 21 children served as a control group." Comment: inadequate information provided
Allocation concealment (selection bias)	Unclear risk	Comment: inadequate information provided
Blinding (performance bias and detection bias) Blinding of Participants	Unclear risk	Comment: inadequate information provided
Blinding (performance bias and detection bias) Blinding of provider	Unclear risk	Comment: inadequate information provided
Blinding (performance bias and detection bias) Blinding of outcome assessor	Unclear risk	Comment: inadequate information provided
Incomplete outcome data (attrition bias)	High risk	Quote: "Due to the absence of some children at the different time points the number of data available for statistical analysis was less than the total number of children involved in this study . . . the number of children from whom complete data sets could be collected was rather low." Comment: no comprehensive data given on lost to follow‐up nor reasons for loss
Selective reporting (reporting bias)	High risk	Comment: does not report data on serum retinol levels, which were collected/measured
Other bias	Unclear risk	Comment: inadequate information provided