This study will investigate in detail the immunological consequences of giving DTP or MV alone or at the same time. The study will involve an intervention trial to analyse the effect of giving DTP with MV on the generation of T cell memory (effector and central), humoral responses, pro-inflammatory cytokine profile (Th1, Th2, Th17) and Treg responses to measles and recall antigens. Our detailed immunological studies will provide vital immunological data on potential mechanisms of the DTP / MV interaction. A comprehensive understanding of the immunological effects of administering either DTP alone or DTP and MV simultaneously will help us understand why these interventions might be detrimental, and may suggest the need to refine current EPI practices. It is also crucial to gain a detailed understanding of the immunological effects of possible deleterious interactions between the current EPI vaccines, before introducing new vaccines that are becoming available for testing in early life e.g. TB and malaria vaccines. Furthermore, understanding mechanisms whereby MV provides survival benefits might identify strategies that can be harnessed in future vaccine design.