Global and national influenza-associated hospitalization and mortality rates: a systematic review and meta-analysis
Bibliographic record
Abstract
Summary Background A global comprehensive assessment of influenza-associated hospitalization and mortality across diverse populations and geographical settings is currently lacking. To support an update of WHO influenza clinical guidelines, this systematic review and meta-analysis evaluated the baseline risks of hospitalization and all-cause mortality in patients with seasonal, pandemic, or zoonotic influenza. Methods We systematically searched Medline, Embase, CENTRAL, CINAHL, and Global Health for studies published through 26 October 2023, that reported hospitalization and/or mortality among patients with laboratory-confirmed influenza. Paired reviewers independently identified studies, extracted data, and assessed the risk of bias. We performed inverse variance method fixed effects model meta-analyses to summarize the evidence and evaluated the certainty of evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. We registered the protocol with PROSPERO, CRD42023456645. Findings Of 30054 records, 355 studies with 18,640,366 patients (mean age 0.1 to 87.9 years) proved eligible. The hospitalization rate was 1.01% (95%CI 1% to 1.01%; moderate certainty) for patients with seasonal or pandemic influenza and 93.72% (95%CI 90.12% to 96.58 %; low certainty) for patients with zoonotic influenza. The all-cause mortality rate was 0.23% (95%CI 0.22% to 0.24%; high certainty) for patients with non-severe seasonal or pandemic influenza, 4.15% (95%CI 4.10% to 4.20%; moderate certainty) for patients with severe seasonal or pandemic influenza, and 38.72% (95%CI 36.79% to 40.66%; moderate certainty) for patients with zoonotic influenza. Interpretation This review estimated a hospitalization rate of 1.01% for seasonal or pandemic influenza and all-cause mortality rates of 0.23% for non-severe seasonal or pandemic influenza, 4.15% for severe seasonal or pandemic influenza, and 38.72% for severe zoonotic influenza. Funding World Health Organization to McMaster University in 2023. Research in context Evidence before this study A comprehensive understanding of influenza-associated hospitalization and mortality rates is essential for guiding effective prevention and control strategies and formulating evidence-based clinical practice guidelines and policies. Previous systematic reviews and meta-analyses have investigated influenza-associated hospitalization and mortality rates, but they have often been limited by their focus on a specific strain of influenza, particular patient subgroups, or individual countries, or by a lack of assessment of the certainty of evidence. A global comprehensive assessment of influenza-associated hospitalization and mortality rates across diverse strains, populations, and geographical settings is currently lacking. Added value of this study We found a hospitalization rate of 1.01% for seasonal or pandemic influenza and all-cause mortality rates of 0.23% for non-severe seasonal or pandemic influenza, 4.15% for severe seasonal or pandemic influenza, and 38.72% for zoonotic influenza. Among severe seasonal or pandemic influenza cases, patients aged ≥65 years (8.31%) had a higher all-cause mortality rate than those aged 0-14 years (0.76%) and 15-64 years (6.50%). Implications of all the available evidence Our study provides a comprehensive assessment of the global evidence regarding hospitalization and mortality rates among influenza patients. Our findings highlight the critical need for distinct clinical and public health strategies tailored to influenza type and severity.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.021 | 0.047 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.023 | 0.047 |
| Bibliometrics | 0.009 | 0.008 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".