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. 2022 Dec 27;10(1):ofac664.
doi: 10.1093/ofid/ofac664. eCollection 2023 Jan.

Burden of Severe Illness Associated With Laboratory-Confirmed Influenza in Adults Aged 50-64 Years, 2010-2011 to 2016-2017

Philip Kim  1 , Brenda Coleman  1   2 , Jeffrey C Kwong  2   3   4   5 , Agron Plevneshi  1 , Kazi Hassan  1 , Karen Green  1 , Shelly A McNeil  6 , Irene Armstrong  7 , Wayne L Gold  8 , Jonathan Gubbay  5   9 , Kevin Katz  9   10 , Stefan P Kuster  11 , Reena Lovinsky  12 , Larissa Matukas  9   13 , Krystyna Ostrowska  14 , David Richardson  15 , Allison McGeer  1   2   9
Affiliations

Burden of Severe Illness Associated With Laboratory-Confirmed Influenza in Adults Aged 50-64 Years, 2010-2011 to 2016-2017

Philip Kim et al. Open Forum Infect Dis. .

Erratum in

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.

Keywords: adult; chronic comorbidity; hospitalization; influenza; mortality.

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Conflict of interest statement

Potential conflicts of interest. S. A. M. reports grant and clinical trials funding from GSK, Merck, Pfizer and Sanofi, and payments from GSK, Pfizer, Sanofi, and Merck outside the submitted work. B. C. reports payments from Seqirus outside the submitted work. A. J. M. reports grant funding from Pfizer, Sanofi and Seqirus, and payments from GSK, Merck, Moderna, Pfizer, and Sanofi outside of the submitted work. All other authors report no potential conflicts.

Figures

Figure 1.
Figure 1.
Incidence of hospitalization (A) and in-hospital mortality (B) in 50- to 64-year-old residents of Toronto and Peel region with laboratory-confirmed influenza, by age group and influenza season. Incidence for those aged 50-54 years is shown in solid grey bars, for those 55-59 years in solid black bars and for those aged 60-65 years in striped bars.
See this image and copyright information in PMC

References

    1. Centers for Disease Control and Prevention. Disease burden of influenza—estimated range of annual burden of flu in the U.S. from 2010 to 2020. 2022. https://www.cdc.gov/flu/about/burden/index.html. Accessed 14 June 2022.
    1. Centers for Disease Control and Prevention. Who is at high risk for flu complications—flu and people 65 years and older. 2022. https://www.cdc.gov/flu/highrisk/65over.htm. Accessed 14 June 2022.
    1. European Centre for Disease Prevention and Control . Risk groups for severe influenza. 2022. https://www.ecdc.europa.eu/en/seasonal-influenza/prevention-and-control/...Accessed 14 June 2022.
    1. Public Health Agency of Canada . Flu (influenza): for health professionals—risk groups for influenza-related complications.2022. https://www.canada.ca/en/public-health/services/diseases/flu-influenza/h.... Accessed 14 June 2022.
    1. The World Health Organization . Seasonal influenza vaccine, weekly epidemiological record. Weekly Epidemiological Record = Relevé épidémiologique hebdomadaire2012; 87:201–16. Available at: https://apps.who.int/iris/handle/10665/241921. Accessed 14 June 2022.