Abstract

Background

Understanding the burden of influenza is necessary to optimize recommendations for influenza vaccination. We describe the epidemiology of severe influenza in 50- to 64-year-old residents of metropolitan Toronto and Peel region, Canada, over 7 influenza seasons.

Methods

Prospective population-based surveillance for hospitalization associated with laboratory-confirmed influenza was conducted from September 2010 to August 2017. Conditions increasing risk of influenza complications were as defined by Canada's National Advisory Committee on Immunization. Age-specific prevalence of medical conditions was estimated using Ontario health administrative data. Population rates were estimated using Statistics Canada data.

Results

Over 7 seasons, 1228 hospitalizations occurred in patients aged 50–64 years: 40% due to A(H3N2), 30% A(H1N1), and 22% influenza B. The average annual hospitalization rate was 15.6, 20.9, and 33.2 per 100 000 in patients aged 50–54, 55–59, and 60–64 years, respectively; average annual mortality was 0.9/100 000. Overall, 33% of patients had received current season influenza vaccine; 963 (86%) had ≥1 underlying condition increasing influenza complication risk. The most common underlying medical conditions were chronic lung disease (38%) and diabetes mellitus (31%); 25% of patients were immunocompromised. The average annual hospitalization rate was 6.1/100 000 in those without and 41/100 000 in those with any underlying condition, and highest in those with renal disease or immunocompromise (138 and 281 per 100 000, respectively). The case fatality rate in hospitalized patients was 4.4%; median length of stay was 4 days (interquartile range, 2–8 days).

Conclusions

The burden of severe influenza in 50- to 64-year-olds remains significant despite our universal publicly funded vaccination program. These data may assist in improving estimates of the cost-effectiveness of new strategies to reduce this burden.

Details

Title
Burden of Severe Illness Associated With Laboratory-Confirmed Influenza in Adults Aged 50–64 Years, 2010–2011 to 2016–2017
Author
Kim, Philip 1 ; Coleman, Brenda 1 ; Kwong, Jeffrey C 2 ; Agron Plevneshi 1 ; Kazi Hassan 1 ; Green, Karen 1 ; McNeil, Shelly A 3 ; Armstrong, Irene 4 ; Gold, Wayne L 5 ; Gubbay, Jonathan 6 ; Katz, Kevin 7 ; Kuster, Stefan P 8 ; Lovinsky, Reena 9 ; Matukas, Larissa 7 ; Ostrowska, Krystyna 10 ; Richardson, David 11 ; McGeer, Allison 1 

 Department of Microbiology, Sinai Health System , Toronto , Canada 
 Dalla Lana School of Public Health, University of Toronto , Toronto , Canada 
 Department of Medicine, Dalhousie University , Halifax , Canada 
 Toronto Public Health , Toronto , Canada 
 Department of Medicine, University Health Network, University of Toronto , Toronto , Canada 
 Public Health Ontario , Toronto , Canada 
 Department of Laboratory Medicine and Pathobiology, University of Toronto , Toronto , Canada 
 Division of Infectious Diseases and Hospital Epidemiology, Cantonal Hospital St Gallen , St Gallen , Switzerland 
 Scarborough Health Network , Toronto , Canada 
10  Trillium Health Partners , Mississauga , Canada 
11  Department of Medical Microbiology and Infectious Diseases, William Osler Health System , Brampton , Canada 
Publication year
2023
Publication date
Jan 2023
Publisher
Oxford University Press
e-ISSN
23288957
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
3170945681
Copyright
© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. This work is published under https://creativecommons.org/licenses/by-nc-nd/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.