High-dose vitamin A to children above 6 months of age reduces all-cause mortality by 23-30%. The WHO recommends vitamin A supplementation (VAS) with the first vaccine after 6 months of age. However, the effect of providing VAS with vaccines has never been investigated. We have hypothesised that the effect of VAS depends on the immune stimulus at the time of supplementation. Hence, the effect might vary depending on which type of vaccine it is given with. In particular, we hypothesised that VAS might be beneficial when given with measles vaccine but not when given with DTP vaccine. Normally the first vaccine after 6 months of age would be a measles vaccine, but many children come late for their DTP vaccinations and receive DTP alone or together with measles vaccine. Hence, it is important to study whether the effect of VAS is the same irrespective of the vaccine(s) administered at the same time.