Rahman 2001.

Methods	Individually randomised study conducted in an urban area of Bangladesh
Participants	Eligibility: children aged 12‐35 months were eligible for inclusion in the study. Children who had received vitamin A within the previous 4 months; had severe malnutrition, with signs or symptoms of vitamin A or zinc deficiency; or with any systemic illness such as diarrhoea, respiratory infection, fever, or any other illness that warranted medical intervention at the time of enrolment were excluded. Sample: 800 children were enrolled (200 in each of the 4 treatment groups). Mean age of participants was between 23.5 and 24.2 months across the treatment groups. 56% of the participants were boys
Interventions	There were 4 treatment groups: Group I: vitamin A 200,000 IU (60 mg) given as a single capsule at day 14, with placebo syrup daily for 14 days Group II: placebo capsule at day 14 and placebo syrup for 14 days Group III: vitamin A 200,000 IU (60 mg) given as a single capsule at day 14, with zinc syrup daily for 14 days Group IV: zinc syrup daily for 14 days, placebo capsule at day 14 Study duration: 6 months
Outcomes	Diarrhoea, acute respiratory infections, serum vitamin A levels, and vitamin deficiency
Notes	Data on treatment analysis was not presented. We have written to authors for data on each treatment arm.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The children were randomly assigned by a person not involved in the study who used permuted blocks of random numbers." Comment: probably done
Allocation concealment (selection bias)	Low risk	Quote: "Sets of 2 bottles and 1 capsule for each child were serially numbered . . . A local pharmaceutical company prepared the study syrups (zinc and placebo) which were supplied in identical 50‐mL bottles . . . The vitamin A and placebo capsules looked identical." Comment: probably done
Blinding (performance bias and detection bias) Blinding of Participants	Low risk	Quote: "The zinc and placebo syrups were supplied in bottles that looked identical, and the appearance and consistency of the syrups were similar. Vitamin A and placebo capsules were identical in appearance." Comment: probably done
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "The randomisation code was kept sealed until the completion of the study." Comment: identical presentation; probably done
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "The treatment allocations were disclosed after the final analysis."
Incomplete outcome data (attrition bias)	Low risk	Comment: data on loss to follow‐up given and also stated that the baseline characteristics of children who were excluded or lost to follow‐up were comparable to those of the children who continued in the study.
Selective reporting (reporting bias)	Unclear risk	Comment: protocol not available
Other bias	Low risk	Comment: no other apparent bias