Ahead of World Pneumonia Day (Sat Nov. 12 ), the first study to provide global estimates of seasonal influenza in children aged under five years and the resultant burden of influenza-related pneumonia is published Online First by the Lancet. The study estimates that, globally, around 90 million children contract seasonal flu each year, causing around 1 million hospital admissions and as many as 111500 deaths due to influenza-related pneumonia—with 99% of these deaths in developing countries. The Article is by Dr Harish Nair, Centre for Population Health Sciences, Medical School, The University of Edinburgh, UK, and colleagues worldwide.
Recent estimates of global pneumonia incidence and mortality associated with Streptococcus pneumoniae, Haemophilus influenzae type b, and respiratory syncytial virus (RSV) do not fully explain the paediatric pneumonia burden, and so the role of other pathogens needs to be explored. These include influenza virus, which is associated with a large but unknown number of hospital admissions in young children globally and is vaccine preventable. Many data for incidence and mortality from influenza-associated pneumonia in developing countries remain unpublished. Therefore, the authors formed an international Influenza Study Group to supplement their systematic literature review (containing published data from high-income and developing countries) with available unpublished data.
The authors identified 43 suitable studies, with data for around 8 million children. They estimated that some 90 million new cases of influenza occurred in children under 5 years worldwide, and 20 million cases of influenza-associated pneumonia, which comprise some 13% or one in eight cases of all paediatric pneumonia globally. Some 1 million cases of influenza-associated severe pneumonia were estimated, comprising 7% or one in 14 of all severe paediatric pneumonia cases worldwide. The authors also estimated there were between 28 000 and 111 500 deaths in children younger than 5 years attributable to influenza-associated pneumonia in 2008, with 99% of these deaths occurring in developing countries. Incidence and mortality varied substantially from year to year in any one setting. Furthermore, there were insufficient data to provide global incidence estimates by type or subtype of influenza virus, although incidence of influenza A was generally higher than was that for influenza B.
The authors conclude: "Influenza is the second most common pathogen identified in children with acute lower respiratory infection [pneumonia] and contributes substantially to the burden of hospitalisation and mortality in young children. Our estimates should inform public health policy and vaccine strategy, especially in developing countries. Our report should also help inform donor agencies in assigning funding priorities for novel vaccine development and implementation or other influenza prevention strategies. Until the widespread implementation of an effective influenza vaccine is achievable, reliable provision of effective case management (including oxygen therapy for hypoxaemia and antibiotic treatment of secondary bacterial infections) will substantially reduce sequelae and mortality associated with this disease."
In a linked Comment, Dr Maria Zambon, Health Protection Agency, London, UK, says: "Importantly, Nair and colleagues' study concludes that most childhood mortality occurs outside of hospital settings, with roughly 15-fold differences of case fatality ratio between developing and developed countries. Most of the world's children live in the developing world. This finding is confirmation of the high disease burden caused by influenza in the youngest age groups, even if the exact numbers are obscure."
She adds that priorities for health interventions need to be ranked, with local evidence to inform decision making, and concludes: "Robust, evidence-based comparisons of health interventions, such as selective versus universal vaccination policies between different countries and regions, are essential to help decision makers with restricted resources who are trying to get the best return for the lowest cost."
For Dr Harish Nair, Centre for Population Health Sciences, The University of Edinburgh, Medical School, UK, please contact Eleanor Cowie, Press Office. T) 44-131-650-6514 / 44-7791-355-886 E) Eleanor.Cowie@ed.ac.uk / harish.nair@ed.ac.uk
For Dr Maria Zambon, Health Protection Agency, London, UK, please contact via press office. T) 44-208-327-7901 / Out of hours 44-208-200-4400 E) colindale-pressoffice@hpa.org.uk
Journal
The Lancet