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Influenza vaccination and 1-year risk of myocardial infarction, stroke, heart failure, pneumonia, and mortality among intensive care unit survivors aged 65 years or older: a nationwide population-based cohort study



We examined whether influenza vaccination affects 1-year risk of myocardial infarction, stroke, heart failure, pneumonia, and death among intensive care unit (ICU) survivors aged ≥ 65 years.


Danish Intensive Care Database data on all elderly ( ≥ 65 years) patients hospitalized in Danish ICUs in the period 2005–2015, and subsequently discharged, were linked with data from other medical registries, including data on uptake of the seasonal influenza vaccine. We computed these patients’ 1-year risk of hospitalization for myocardial infarction, stroke, heart failure, or pneumonia, and their 1-year risk of all-cause mortality. Hazard ratios (HRs) with 95% confidence intervals (CIs) were computed using Cox proportional hazards regression, with adjustment and propensity score matching applied to handle confounding.


The study included 89,818 ICU survivors. The influenza vaccinated patients (n = 34,871, 39%) were older, had more chronic diseases, and used more prescription medications than the unvaccinated patients. Adjusted 1-year mortality was decreased among the vaccinated versus the unvaccinated patients (19.3% versus 18.8%; adjusted HR, 0.92; 95% CI 0.89–0.95). Influenza vaccination was also associated with a decreased risk of stroke (adjusted HR, 0.84; 95% CI 0.78–0.92), but only a small, non-significantly decreased risk of myocardial infarction (adjusted HR, 0.93; 95% CI 0.83–1.03). There was no association between vaccination and subsequent hospitalization for heart failure or pneumonia. Propensity score matched analyses confirmed these findings.


Compared with the unvaccinated ICU survivors, the influenza vaccinated ICU survivors had a lower 1-year risk of stroke and a lower 1-year risk of death, whereas no substantial association was observed for the risk of hospitalization for myocardial infarction, heart failure, or pneumonia. Our findings support influenza vaccination of individuals aged ≥ 65 years.

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This research received financial support from the Danish Medical Research Council (Grant 271-05-0511), from the Aarhus University Research Foundation, and from the Program for Clinical Research Infrastructure (PROCRIN) established by the Lundbeck Foundation and the Novo Nordisk Foundation and administered by the Danish Regions. The funding agencies had no role in the design, conduct, analysis, or reporting of this study.

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CFC, RWT, MS, and HTS conceived the study idea and designed the study. CFC and HTS obtained the funding. CFC and LP collected the data and carried out the analyses. CFC organized the writing and wrote the first draft. All authors participated in the discussion and interpretation of the results. All authors critically revised the manuscript for intellectual content and approved the final version before submission. CFC is the guarantor.

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Correspondence to Christian Fynbo Christiansen.

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Christiansen, C.F., Thomsen, R.W., Schmidt, M. et al. Influenza vaccination and 1-year risk of myocardial infarction, stroke, heart failure, pneumonia, and mortality among intensive care unit survivors aged 65 years or older: a nationwide population-based cohort study. Intensive Care Med 45, 957–967 (2019).

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  • Cardiovascular diseases
  • Cohort studies
  • Infection
  • Influenza vaccines
  • Intensive care
  • Mortality