Ramakrishnan 1995.

Study characteristics
Methods	Individually randomised trial conducted in rural India
Participants	Eligibility: children aged 6–36 months Excluded: children with ophthalmic signs of xerophthalmia, serious diseases, or severe malnutrition (< 60% of weight‐for‐age or < 85% of height‐for‐age of the National Center for Health Statistics median), who received appropriate treatment, including vitamin A Sample: 583 children; 309 in vitamin A group, 274 in placebo group. Mean age 18.6 months. 49.9% boys
Interventions	Experimental group: vitamin A 100,000 IU for children aged < 1 year and 200,000 IU for children aged > 1 year Control group: placebo Study duration: interventions given every 4 months for 12 months
Outcomes	Incidence of diarrhoea and respiratory disease
Notes	Definition used for respiratory disease was too generalised to be included under LRTI. It mainly covered upper respiratory tract infections.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The study design was a randomised, double‐blind, placebo controlled intervention trial in which every 4 mo [months] the treatment group received a high‐dose vitamin A supplement and the control group received a placebo". Comment: insufficient detail provided.
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information to permit judgement.
Blinding (performance bias and detection bias) Blinding of participants	Low risk	Quote: "The study design was a randomised, double‐blind, placebo controlled intervention trial in which every 4 mo the treatment group received a high‐dose vitamin A supplement and the control group received a placebo". Comment: statement that blinding occurred, no further details provided.
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "The study design was a randomised, double‐blind, placebo controlled intervention trial in which every 4 mo the treatment group received a high‐dose vitamin A supplement and the control group received a placebo". Comment: statement that blinding occurred, no further details provided.
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "The study design was a randomised, double‐blind, placebo controlled intervention trial in which every 4 mo the treatment group received a high‐dose vitamin A supplement and the control group received a placebo". Comment: statement that blinding occurred, no further details provided.
Incomplete outcome data (attrition bias)	Low risk	Quote: "Out of the 660 children who were eligible, a final group of 592 children who had both pre‐ and post‐anthropometric measurements were used in this analysis. The losses at follow‐up due to migration (n = 50), death (n = 10) and incomplete measurements (n = 8) were similar for both groups". Comment: losses were not large and balanced between groups; unlikely to introduce substantial bias here. Clinically relevant impact unlikely.
Selective reporting (reporting bias)	High risk	Quote: "The examination for ophthalmic signs of vitamin A deficiency, using WHO criteria (27), was conducted by trained ophthalmologists from the Department of Ophthalmology, CMCH, at baseline and at the end of the 1‐y follow‐up period. Blood samples were also taken (from finger pricks) at the beginning and the end of the study by using 250‐pt capillary tubes. Serum retinol concentrations were estimated by using reversed‐phase HPLC at the Wellcome Research Laboratory, CMCH, Vellore, using retinyl acetate and all trans‐retinol (Sigma Chemical Co, St Louis) as standards". Comment: though measured, serum retinol results were not reported.
Other bias	Low risk	Comment: no other apparent bias.