Epidemiology and Infection

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Epidemiology and Infection (2010), 138:1542-1549 Cambridge University Press
Copyright © Cambridge University Press 2010
doi:10.1017/S0950268810000579

For Debate

Influenza

Age, influenza pandemics and disease dynamics


A. L. GREERa1a4, A. TUITEa1 and D. N. FISMANa1a2a3 c1

a1 Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
a2 Department of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada
a3 Department of Medicine, University of Toronto, Toronto, ON, Canada
a4 Public Health Agency of Canada, Ottawa, ON, Canada
Article author query
greer al [PubMed]  [Google Scholar]
tuite a [PubMed]  [Google Scholar]
fisman dn [PubMed]  [Google Scholar]

SUMMARY

The world is currently confronting the first influenza pandemic of the 21st century [caused by a novel pandemic influenza A (H1N1) virus]. Earlier pandemics have been characterized by age distributions that are distinct from those observed with seasonal influenza epidemics, with higher attack rates (and correspondingly increased proportionate or relative mortality) in younger individuals. While the genesis of protection against infection in older individuals during a pandemic is uncertain, differential vulnerability to infection by age has important implications for disease dynamics and control, and for choice of optimal vaccination strategies. Age-related vulnerability to infection may explain differences between school- and community-derived estimates of the reproductive number (R) for a newly emerged pandemic strain, and may also help explain the failure of a newly emerged influenza A (H1N1) virus strain to cause a pandemic in 1977. Age-related factors may also help explain variability in attack rates, and the size and impact of influenza epidemics across jurisdictions and between populations. In Canada, such effects have been observed in the apparently increased severity of outbreaks on Indigenous peoples' reserves. The implications of these patterns for vaccine allocation necessitate targeted research to understand age-related vulnerabilities early in an influenza pandemic.

(Accepted February 17 2010)

(Online publication March 22 2010)

Key Words:Epidemiology; infectious disease dynamics; influenza; mathematical modelling

Correspondence:

c1 Author for correspondence: D. N. Fisman, MD, MPH, FRCPC, Dalla Lana School of Public Health, 155 College Street, Room 678, Toronto, Ontario, Canada M5T 3M7. (Email: david.fisman@utoronto.ca)


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