18 November 2011
Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis
Influenza is a common pathogen identified in children with acute lower respiratory infections (ALRI) and results in a substantial burden on health services. However, the global burden of disease attributable to seasonal influenza virus in children has been unknown. In this study, Nair et al. estimate the global incidence of influenza episodes, influenza-associated ALRI, and influenza-associated severe ALRI in children younger than 5 years, stratified by age. The investigators pooled data from 43 independent population-based studies around the world carried out in the time period January 1, 1995 to October 31, 2010. The pooled studies contained information for about 8 million children. The authors estimate that there are annually:
• 90 million (95% CI 49—162 million) new cases of influenza;
• 20 million (95% CI 13—32 million) cases of influenza-associated ALRI;
• 1 million (95% CI 1—2 million) cases of influenza-associated severe ALRI (7% of cases of all severe pediatric ALRI)
The authors did not find that there were sufficient data to yield accurate estimates for the number of annual pediatric deaths as only a small number of studies had useful mortality data. However, based on these limited data, they estimated that at least 28,000 to 111,500 deaths occur in children younger than 5 years attributable to influenza-associated ALRI per year, with 99% of these deaths occurring in developing countries.
The authors also noted that incidence and mortality varied substantially between years in any one setting.
Influenza is a common pathogen identified in children with lower respiratory track infections and results in a substantial burden of disease which is often underappreciated by both health care providers and the general public. The finding of 20 million annual episodes of severe lower respiratory tract disease related to influenza would indicate that influenza occurs at a level comparable to both Streptococcus pneumoniae (about 13.8 million episodes of pneumonia per year), Hemophillus influenza type B (about 7.9 million episodes of pneumonia per year), organisms for which pediatric vaccination is widely accepted. The further development of surveillance capacity is needed, particularly in developing countries where data continue to be limited, to aid policy makers and the global community to better understand the true impact of this disease. In addition, more research into the effective use of influenza vaccine in this age group is needed along with data on the economic burden to assist policy makers in evidence-based decision making regarding measures to prevent or treat influenza.
Nair, H. et al. 2011. Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis. The Lancet; doi:10.1016/S0140-6736(11)61051-9).
O'Brien KL, Wolfson LJ, Watt JP, Henkle E, Deloria-Knoll M, McCall N, et al. Burden of disease caused by Streptococcus pneumoniae in children younger than 5 years: global estimates. The Lancet. 2009; 374(9693): 893-902.
Watt JP, Wolfson LJ, O'Brien KL, Henkle E, Deloria-Knoll M, McCall N, et al. Burden of disease caused by Haemophilus influenzae type b in children younger than 5 years: global estimates. The Lancet. 2009; 374(9693): 903-11.