 The sample size is 400 subjects 200 in group 1 and 200 in group 2. It will be an open-label, randomized, multi-centre study in which group 1 will receive Td5ap as a single injection and group 2 will receive Td1aP as a single injection. DTP antibodies will be measured before and 28 days 14 days after Td5ap and Td1aP vaccination. The proportion of children with positive IgG antibody response will be measured in each study arm. Sera will be tested blindly by established ELISA methods and saliva samples will be analyzed by exploratory assays. In a subpopulation cellmediated immunity will be analyzed. The safety evaluation criteria will be the percentage of subjects with adverse events describing injection-site adverse reactions, systemic adverse events, daily temperatures and serious adverse events. 