Estimates for 2015 suggest that 5.9 million children worldwide died before reaching the age of five, including 2.7 million newborns. Globally, four million (4.02 million) fewer child deaths occurred in 2015 than in 2000, mainly thanks to reductions in deaths from pneumonia, diarrhoea, death during birth, malaria and measles. However, progress on reducing newborn deaths (in the first 28 days) has been slower meaning that as a whole the world failed to reach the Millennium Development Goal (MDG) target of reducing child deaths by two-thirds between 1990 and 2015.
The study, published in The Lancet, provides the most up-to-date figures for deaths of children under five years old and includes data for all 194 countries that are World Health Organisation states (see appendix 6 for country-level data). The 2015 figures highlight the inequality in child deaths around the world with the national rates of child death ranging from 1.9 to 155.1 deaths per 1000 births, and 60.4% (3.6 million) of all deaths occurring in 10 countries.
Progress since 2000 has largely been due to reductions in the rates of deaths from pneumonia, diarrhoea, malaria, measles and deaths during birth - each reduced by more than 30% worldwide between 2000 and 2015 (see figure 2). However, some of these still remain leading causes of deaths. Globally in 2015, the leading causes of death for children under five years old were complications due to premature birth (17.8%, 1.1 million deaths), pneumonia (15.5%, 0.9 million deaths) and death during birth (11.6%, 0.7 million deaths).
Countries with the highest rates of child death (100 or more deaths per 1000 births) include Angola, Central African Republic, Chad, Mali, Nigeria, Sierra Leone and Somalia. In these countries pneumonia, malaria and diarrhoea were the leading causes of death (see figure 3), so to improve survival in these regions the researchers recommended improving the uptake of breastfeeding, providing vaccines for pneumonia, malaria and diarrhoea, and improving water and sanitation.
In comparison, for countries with the lowest rate of child death (less than 10 deaths per 1000 births) which include the Russian Federation and the United States of America, the leading causes of death include congenital abnormalities, complications due to premature birth and injuries (see figure 3). Improved detection and surgery for congenital abnormalities, better medical care during pregnancy and childbirth, and more research on effectiveness of injury interventions could help improve survival in these countries.
Although the number of newborn deaths was reduced from 3.9 million in 2000 to 2.7 million in 2015 (see appendix 6), progress has been slower than the improvements in survival for one month to five year olds. This resulted in the proportion of newborn deaths increasing from 39.3% in 2000 to 45.1% in 2015. If newborn deaths had reduced at the same rate as that of children aged between one month and five years old the MDG target to reduce child deaths by two-thirds between 1990 to 2015 might have been reached.
"Child survival has improved substantially since the Millennium Development Goals were set even though the target to reduce child deaths by two-thirds was not achieved" says Dr Li Liu, lead author, Johns Hopkins Bloomberg School of Public Health, USA. "The problem is that this progress is uneven across all countries, meaning a high child death rate persists in many countries. Substantial progress is needed for countries in sub-Saharan Africa and Southern Asia to achieve the child survival target of the Sustainable Development Goals." 
The model used in the study provides estimates based on vital registration data and from high quality literature on causes of child deaths. It used statistical analysis to estimate figures for countries with poor data collection due to there being fewer birth and death registries.
Writing in a linked Comment, Professor Peter Byass, Umeå Centre for Global Health Research says "Undoubtedly child mortality is falling, and the world should be proud of this progress" but he adds "... Of the estimated six million under-5 child deaths in 2015, only a small proportion were adequately documented at the individual level, with particularly low proportions evident in low-income and middle-income countries, where most childhood deaths occur... That six million under-5 children continue to die every year in our 21st century world is unacceptable, but even worse is that we seem collectively unable to count, and hence be accountable for, most of those individual deaths."
NOTES TO EDITORS
The study was funded by the Bill & Melinda Gates Foundation and the World Health Organization. It was conducted by the Johns Hopkins Bloomberg School of Public Health, The London School of Hygiene and Tropical Medicine, the World Health Organisation, The China National Office of Maternal and Child Health Surveillance and Sichuan University.
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