Vaccine responses are impaired in many low- and middle-income countries. Given that many of the world’s poorest children will be malnourished at the points they receive their childhood vaccinations, an interaction between nutrition and vaccine response is likely. Further, there is now evidence that vaccines have substantial nonspecific effects in children in high-mortality regions, and that these effects may be exaggerated when vaccines are given in parallel to vitamin A supplements (VAS). Through our ongoing trial of neonatal VAS, we will investigate the mechanisms through which VAS and vaccines interact on immune function. In this programme of work we will assess the impact of nutritional supplementation on infant antibody responses.