Biswas 1994.

Study characteristics
Methods	Individually randomised, placebo‐controlled trial conducted in Gobinda‐Khatick slum area of eastern Kolkata (formerly Calcutta), India
Participants	Eligibility: children aged 12–71 months Excluded: children with signs of VAD (e.g. xerophthalmia) Sample: 180 children. Mean age and proportions of boys not specified
Interventions	Experimental group: single‐dose vitamin A 200,000 IU in form of retinyl palmitate Control group: placebo Follow‐up: 6 months
Outcomes	Incidence of diarrhoea and acute respiratory tract infection
Notes	The baseline age and nutritional characteristics were similar in both the groups. The surveillance for morbidity outcomes was performed twice monthly. For respiratory disease morbidity, we used data for LRTI only.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "For each strata, a restricted randomisation list was prepared … a random permutated block of block length 6 was used". Comment: block randomisation by age and weight; probably done.
Allocation concealment (selection bias)	Low risk	Quote: "… randomisation was done by a pharmacist of the drug manufacturing company". Comment: assuming that the pharmacist was independent of the study team, this was probably adequate.
Blinding (performance bias and detection bias) Blinding of participants	Low risk	Quote: "… identical (colour and taste) placebo. Both drug and placebo were prepared and dispensed in a single dose amber coloured glass ampoule by a local pharmaceutical company".
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Quote: "For keeping the trial totally blinded to all participants (for example, patients, investigators, surveyor), randomisation was done by a pharmacist of the drug manufacturing company. Samples of drug (or placebo) were identified by the code number of the respective child".
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Quote: "For keeping the trial totally blinded to all participants (for example, patients, investigators, surveyor), randomisation was done by a pharmacist of the drug manufacturing company. Samples of drug (or placebo) were identified by the code number of the respective child".
Incomplete outcome data (attrition bias)	Low risk	Quote: "… data was analysed for 174 children due to attrition of 6 children for various reasons (for example, 5 children were hospitalised due to illnesses unrelated to the study objectives and the death of 1 child due post‐measles bronchopneumonia)". Comment: attrition was low and reported as unrelated to treatment.
Selective reporting (reporting bias)	Unclear risk	Comment: study protocol was not available to permit a clear judgement. Study aims were to measure diarrhoea and respiratory infection; both outcomes were reported in full in the study report. 1 child died and the treatment group assignment was not disclosed.
Other bias	Low risk	Comment: study appeared free of other bias.