Discussion with the guideline group members and the External Experts and Stakeholders Panel highlighted the limited evidence in some areas, meriting further research on vitamin A supplementation in infants and children 6–59 months of age, in particular, in the following areas:

• effect of different doses of vitamin A on the critical outcomes of morbidity and mortality, and stratification of the data by sex, length of follow-up, vaccination status and subsequent vitamin A supplementation;
• the role of vitamin A supplementation in countries with high measles immunization rates and its effect on measles-related mortality;
• comparative analysis of the different delivery mechanisms of vitamin A (capsules versus droppers for delivery of supplemental vitamin A, food fortificants);
• identification of field-friendly clinical and biochemical indicators of vitamin A status and vitamin A stores;
• co-interventions that may interact with vitamin A, for example other nutrients (such as vitamin D) and vaccines (such as diphtheria, tetanus, polio).