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Meta-Analysis
. 2025 Mar;19(3):e70073.
doi: 10.1111/irv.70073.

Mortality Risk Among Patients With Influenza Illness Admitted to the ICU: A Systematic Review and Meta-Analysis

Pablo Suárez-Sánchez  1 , Jara Majuelos-Melguizo  1 , Marina Hinojosa-Campos  1 , Bélène Podmore  1 , Iain A Gillespie  2 , Jennifer Han  3 , Rosa Sloot  4 , Dina Christensen  3
Affiliations
Meta-Analysis

Mortality Risk Among Patients With Influenza Illness Admitted to the ICU: A Systematic Review and Meta-Analysis

Pablo Suárez-Sánchez et al. Influenza Other Respir Viruses. 2025 Mar.

Abstract

Background: Despite vaccination programs and available treatments, seasonal influenza carries a large mortality burden, especially in intensive care unit (ICU) settings. Understanding the influenza mortality burden in ICU settings can inform treatment planning and resource allocation. Nonetheless, surveillance data on mortality in ICU-admitted patients are scarce and estimates vary greatly. This systematic literature review (SLR) and meta-analysis investigated all-cause mortality risk among ICU-admitted patients with influenza in Europe.

Methods: We included observational studies conducted in Europe that reported mortality among patients ≥ 6 months of age with influenza admitted to the ICU. Studies published between January-2009 and December-2019 were included. Quality was assessed using a modified Newcastle-Ottawa scale. Pooled all-cause mortality risk was calculated as a proportion using a random-effects model with an inverse variance method. A sensitivity analysis was also conducted, including only studies identified as having low risk of bias.

Results: Thirty-seven studies, reporting on 13,616 patients, were included. All-cause mortality ranged from 0% to 67%. The overall pooled mortality risk estimate was 0.24 (95% CI: 0.20, 0.27). Study heterogeneity was high (Cochran's Q test p < 0.01, I2 = 93%). The sensitivity analysis using only studies identified as having low risk of bias produced a pooled mortality risk of 0.25 (95%CI: 0.21, 0.29).

Conclusions: These results indicate that approximately a quarter of patients with influenza admitted to the ICU die, reinforcing the need for effective vaccination programs and treatment optimization.

Keywords: influenza; intensive care unit; meta‐analysis; mortality; neuraminidase inhibitors.

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Conflict of interest statement

Pablo Suarez‐Sanchez, Jara Majuelos, Marina Hinojosa‐Campos, Bélène Podmore are employees of OXON Epidemiology Ltd Epidemiology & Statistics, Madrid, Spain, an independent contract research organization, which received funding from GSK to design and conduct this study. Iain A Gillespie, Jennifer Han, Rosa Sloot, and Dina Christensen are employees of and may hold shares in the GSK group of companies.

Figures

FIGURE 1
FIGURE 1
PRISMA flowchart for study selection and inclusion.
FIGURE 2
FIGURE 2
Pooled mortality risk among patients with influenza admitted to the ICU.
FIGURE 3
FIGURE 3
Pooled mortality risk among patients with influenza admitted to the ICU in studies with low risk of bias.
See this image and copyright information in PMC

References

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