The under-five mortality rate has fallen in all regions since 1990, and some regions have come close to being on track to meet MDG Target 4.A. However, in most countries, the rate has not declined fast enough to meet the target by 2015, and over three-quarters of countries with available data are not on track. Nearly half of all deaths of children under five occur in Sub-Saharan Africa. Malnutrition, as well as lack of access to water and sanitation infrastructure, contributes to the poor health and death of young children. The leading cause of childhood deaths, including pneumonia, diarrhea, malaria, and measles, can easily be prevented through basic health service improvements and interventions, such as insecticide-treated mosquito nets and vaccinations.