Vijayaraghavan 1990.

Study characteristics
Methods	Cluster‐randomised study in rural India
Participants	Eligibility: children aged 1–5 years Excluded: children with corneal involvement Sample: 15,775 children in 84 clusters. 50.4% boys
Interventions	Experimental group: vitamin A 200,000 IU given twice Control group: placebo (arachis oil) Study duration: unclear
Outcomes	Mortality, diarrhoea, acute respiratory infections, measles
Notes	Respiratory infection has non‐specific definition of "clinically significant cough".
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The villages were allocated randomly into two groups‐treatment and control". Comment: insufficient detail to form a judgement.
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient detail provided.
Blinding (performance bias and detection bias) Blinding of participants	Low risk	Quote: "The trial was double blind: the investigators and medical officers did not know which were the treatment and which were the control areas. They were not aware whether the dose they were distributing was vitamin A or placebo. Decoding was done only after data had been collected".
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Comment: as above; probably done.
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Comment: as above; probably done.
Incomplete outcome data (attrition bias)	Unclear risk	Comment: insufficient detail provided.
Selective reporting (reporting bias)	High risk	Comment: incidence of infections outcome not given with respect to vitamin A and control groups. Given according to the clinical vitamin A status of all the study children.
Other bias	Low risk	Comment: study appeared free of other bias.