Estimates of mortality associated with seasonal influenza for the European Union from the GLaMOR project

Abstract

Background: The European Centres for Disease Prevention and Control (ECDC) estimates that seasonal influenzacauses 4-50 million symptomatic infections in the EU/EEA each year and 15,000-70,000 European citizens die of causes associated with influenza. We used modelling methods to estimate influenza-associated mortality for the European Union by age group and country.

Methods: We compiled influenza-associated respiratory mortality estimates for 31 countries around the world (11 countries in the EU) during 2002-2011 (excluding the 2009 pandemic). From these we extrapolated the influenza mortality burden for all 193 countries of the world, including the 28 countries of the EU, using a multiple imputation approach. To study the effect of vaccination programs, we obtained data from the EU-funded VENICE project regarding the percentage of persons over 65 who were vaccinated in each country; the data ranged from 2% to 82% between the 21 countries which provided estimates for the 2006/07 reference season.

Results: We estimated that an average of 27,600 (range 16,200-39,000) respiratory deaths were associated with seasonal influenza in the 28 EU countries per winter; 88% were among people 65 years and older, and the rates of mortality in this age group were roughly 35 times higher compared with those < 65 years. Estimates varied considerably across the EU; for example, rates in the elderly ranged from 21.6 (12.5-35.1) per 100,000 in Portugal to 36.5 (16.4-62.5) in Luxembourg, a difference of nearly 70%. We were unable to find a negative correlation between vaccination coverage rates and influenza-associated mortality estimates in the elderly.

Conclusion: Our EU estimate of influenza-associated respiratory mortality is broadly consistent with the ECDC estimate. More research is needed to explain the observed variation in mortality across the EU, and on possible bias that could explain the unexpected lack of mortality benefits associated with European elderly influenza vaccination programs.

Keywords: Europe; Influenza; Mortality; Regional; Respiratory Mortality.