Chowdhury 2002.

Study characteristics
Methods	Individually randomised trial conducted in urban slums of Chandigarh, India
Participants	Eligibility: children aged < 10 years Excluded: children with xerophthalmia and history of VAS Sample: 1520 children; 756 to vitamin A group, 759 to placebo group. Mean age 51 months. 50% boys
Interventions	Experimental group: vitamin A 50,000 IU for children aged < 6 months; 100,000 IU for children aged 6–12 months and 200,000 IU for children aged > 1 year Control group: placebo Study duration: intervention given every 4 months for 15 months
Outcomes	All‐cause mortality; cause‐specific mortality due to diarrhoea, pneumonia, and meningitis; incidence of diarrhoea, pneumonia, and measles. Measurement of subclinical VAD status was by conjunctival impression cytology
Notes	Baseline sociodemographic and anthropometric characteristics were similar in both the groups. Study population had a high prevalence of VAD. Children were contacted every 15 days by home visits to obtain information on morbidity and mortality. Study included children aged < 10 years; however, the mean age of the children was 51 months. Study methods were not explicitly described. According to WHO, India is a country with a high child mortality rate (i.e. > 40/1000).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "From three slums of Chandigarh, 1520 non‐xerophthalmic children of less than 10 years of age were individually randomised in equal number to receive vitamin A or placebo".
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information to permit judgement.
Blinding (performance bias and detection bias) Blinding of participants	Unclear risk	Quote: "An equivalent volume of arachis oil was given as placebo". Comment: insufficient information to permit judgement.
Blinding (performance bias and detection bias) Blinding of provider	Unclear risk	Comment: insufficient information to permit judgement.
Blinding (performance bias and detection bias) Blinding of outcome assessor	Unclear risk	Comment: insufficient information to permit judgement.
Incomplete outcome data (attrition bias)	High risk	Comment: although attrition rates were balanced, the rates of mortality were lower than the rate of withdrawal. This could impact on the reliability of the results.
Selective reporting (reporting bias)	Unclear risk	Comment: insufficient information to permit judgement.
Other bias	Unclear risk	Comment: study not sufficiently reported in order to assess this item fully.