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Frequent, earlier influenza vaccinations reduce death risk in HF
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Compared with intermittent and late vaccinations, frequent and earlier influenza vaccinations were associated with larger reductions in risk for death in patients with HF, researchers reported in Circulation.
Researchers assessed the association between influenza vaccinations and survival in a large, nationwide cohort of unselected patients with HF.
Serious threat
“An influenza infection is a serious event for patients with HF,” Daniel Modin, MB, of the department of cardiology at the Herlev and Gentofte Hospital at University of Copenhagen in Denmark, and colleagues wrote. “Although a few observational studies have indicated that influenza vaccination may improve outcomes in heart failure, there have been no randomized control trials to establish benefits among patients with heart failure receiving an influenza vaccine or placebo.”
Researchers identified all patients in Denmark diagnosed with new HF from 2003 to June 2015 (n = 134,048) using the Danish National Patient Registry. Patients who died within 30 days of their HF diagnosis and patients younger than 18 years were excluded from the study.
As influenza vaccinations are recommended by the Danish Health Authority and are offered free to individuals with CVD, including HF, researchers were able to obtain vaccination records through the Danish National General Practitioners Reimbursement Registry and established variables based on the following:
- vaccination exposure based on whether a patient received at least one influenza vaccination within the follow-up period after their diagnosis;
- cumulative number of vaccinations during the follow-up period;
- vaccination frequency during the follow-up period; and
- the time of year for each administered vaccine.
Patients were followed through death, emigration or to the end of the follow-up period. Researchers obtained CV-related deaths using cause-of-death data through Jan. 1, 2016, and all-cause death rates using follow-up data on mortality status available through Jan. 1, 2017.
The primary endpoints were all-cause and CV deaths. Secondary endpoints were incident atrial fibrillation or flutter and a composite outcome consisting of ventricular tachycardia or ventricular fibrillation and cardiac arrest.
The follow-up was 99.8% with a median follow-up time of 3.7 years (interquartile range [IQR], 1.7-6.8). The median follow-up for all-cause death was 3.7 years (interquartile range, 1.7-6.8) and 3.3 years (interquartile range, 1.3-6.3) for CV deaths.
The vaccination coverage of the cohort ranged from 16% to 54% during the study period. Researchers wrote that in the unadjusted analysis, receiving one or more vaccinations during follow-up was associated with a higher risk for death (HR for all-cause mortality = 1.28; 95% CI, 1.26-1.3; HR for CV mortality = 1.26; 95% CI, 1.23-1.28).
Reduced death risk
In a model adjusted for comorbidities, medications, household income and education level, receiving at least vaccination was associated with an 18% reduced risk for all-cause and CV deaths (HR = 0.82; 95% CI 0.81-0.84 for both).
Researchers wrote that annual vaccinations, vaccinations in September or October as opposed to later in the influenza season and a greater cumulative number of vaccinations were associated with larger reduction in the risk for death compared with intermittent vaccination.
The limitations of the study were that researchers only had information on vaccines administered by general practitioners and the lack of clinical variables, including left ventricular ejection and brain natriuretic peptide levels.
“Annual influenza vaccinations may be an effective treatment strategy to improve survival in HF,” Modin and colleagues wrote. – by Earl Holland
Disclosures: Modin was supported by a scholarship from the Danish Heart Foundation during preparation of the manuscript. Please see the study for all other authors’ relevant financial disclosures.
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