Two months after inclusion, the children will have another tuberculin test to examine changes in tuberculin reaction. At the same time, scar-size will be measured. In the initial phase of the project, a finger-prick blood sample will be collected from 1000 children to examine whether BCG boosting/no boosting have had an effect on the prevalence of malaria parasitaemia and the level of measles antibodies. Children with malaria will be treated and children with non-protective levels of measles antibodies will be offered revaccination with measles vaccine. In a group of children, samples will be collected both before and after BCG revaccination/no revaccination to measure changes in cytokine profile. Children with a large PPD reaction (> 15mm) will be followed in a similar way as the other children as this may reflect immune stimulation from exposure to natural TB. The studies of morbidity and immunological changes will be done both in the dry and the rainy seasons. The children will be followed for hospitalisations and mortality to 5 years of age.