Rahmathullah 1990.

Methods	Cluster‐randomised trial conducted in Trichy district of Tamil Nadu in southern India
Participants	Eligibility: children aged 6‐60 months were included in the study. Sample: clustering unit was 'panchyat' (local government areas). 206 clusters were formed, and the majority of them consisted of 50‐100 children. The included clusters had a total of 15,419 children, of whom 7764 were in vitamin A group and 7655 in placebo group.
Interventions	Children in experimental group received weekly doses of 8333 IU vitamin A and 20 mg vitamin E. The control group received 20 IU of vitamin E only in peanut oil. Any children diagnosed with xerophthalmia at baseline, midterm, or final examination were given a high dose (200,000 IU) supplement of vitamin A and continued in the study. Supplementations were given for 52 weeks. Children who missed 7 consecutive dosages were excluded from the analysis.
Outcomes	All‐cause mortality; cause‐specific mortality due to diarrhoea, measles, and respiratory disease; incidence of diarrhoea and respiratory disease morbidity
Notes	The baseline characteristics of the 2 groups were similar in terms of age and sex, 1‐month history of diarrhoea and respiratory disease, anthropometric indexes of nutritional status, xerophthalmia status, 5‐year retrospective history of mortality of children under 5, household economic, household hygienic status, and serum retinol levels. On average > 90% of the children were contacted each week, and the lowest coverage in any single week was 88%. 11% had clinical evidence of xerophthalmia, while about 38% had serum retinol concentrations < 0.35 mmol/L at baseline.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The clusters were arranged according to population size; after a random start, they were assigned alternately to the treated or control groups." Comment: exact method of sequence generation was not provided
Allocation concealment (selection bias)	Low risk	Quote: ". . . no one associated with the study was aware of the colour code, which was held by the Hoffmann‐LaRoche until the study ended."
Blinding (performance bias and detection bias) Blinding of Participants	Low risk	Quote: "The appearance and taste of the solutions were identical . . . no one associated with the study was aware of the colour code, which was held by the Hoffmann‐LaRoche until the study ended." Comment: probably done
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "The appearance and taste of the solutions were identical . . . no one associated with the study was aware of the colour code, which was held by the Hoffmann‐LaRoche until the study ended . . . masked controlled . . ." Comment: probably done
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "The appearance and taste of the solutions were identical . . . no one associated with the study was aware of the colour code, which was held by the Hoffmann‐LaRoche until the study ended . . . masked controlled . . ."
Incomplete outcome data (attrition bias)	Low risk	Quote: "There was no difference in rates of contact between the treated and control groups. The reasons for lack of contact included moving from the study area . . ." Comment: reasons for loss to follow‐up given with a note that there was no difference in contact rates between the 2 groups
Selective reporting (reporting bias)	Low risk	Comment: all important outcomes given in results as mentioned in the Methods section
Other bias	Low risk	Comment: no other apparent bias