Around 90 million children contract seasonal flu every year worldwide, which leads to about one million hospital admissions, claims a new report published today by The Lancet.
The report, timed to coincide with World Pneumonia Day on 12 November, is described as the first study to provide global estimates of seasonal influenza in children aged under five as well as the resulting burden of flu-related pneumonia.
The international team of researchers led by Dr Harish Nair of the Centre for Population Health Sciences at the University of Edinburgh, found that the number of deaths a year due to flu-related pneumonia can reach as high as 111,500. Almost all of those deaths (99%) happen in developing countries.
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, so the authors wanted to explore the role of other causes such as the flu virus.
The authors formed an international Influenza Study Group to supplement their systematic literature review with available unpublished data.
They identified 43 suitable studies, with data for around eight million children published between 1995 and 2010.
The collective results indicated that in 2008, there were an estimated 90 million new cases of flu occurring in children under 5 years worldwide annually, and 20 million cases of flu-associated pneumonia.
Analysis of the results also showed there were between 28,000 and 111,500 deaths in children younger than 5 years attributable to flu-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.
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.”
In an accompanying comment, Dr Maria Zambon of the Health Protection Agency, said: “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.
“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.”