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Getting the flu shot each year is associated with better survival outcomes for heart failure (HF) patients, a large, Danish cohort study found.
After adjustment for education, household income, prescriptions, comorbidities, and inclusion date, patients getting at least one influenza vaccination during the median 3.7 years of follow-up had an 18% lower risk of all-cause mortality (HR 0.82, 95% CI 0.81-0.84) and death from cardiovascular causes (HR 0.82, 95% CI 0.81-0.84).
The more years vaccinated and the earlier in the flu season it was done, the lower the risk of all-cause and cardiovascular death (both P<0.001 for trend), reported Daniel Modin, BSc, Med, of the University of Copenhagen, and colleagues in Circulation.
If causal, the effect would be nearly on par with the 20% to 25% mortality reduction seen with beta-blockers and ACE inhibitors, they noted, although cautioning that their observational findings couldn't prove a direct effect.
Even so, these findings "may well motivate [cardiologists] to refer all their heart failure patients for vaccination to their primary care doctor or to a pharmacy," commented William Schaffner, MD, of Vanderbilt University Medical Center in Nashville, Tennessee.
"Influenza immunization is inexpensive, quick, and I don't think that cardiologists can do anything else to benefit their patients that has the immediate impact that influenza vaccination does or is as cheap. So I think every cardiologist ought to be doing this, starting the day after this paper is published," Schaffner told MedPage Today.
The American College of Cardiology, the American Heart Association, and the European Society of Cardiology encourage the flu shot for HF patients but without a class of recommendation or level of evidence given "due to lack of sufficient evidence," the study authors noted. Some observational studies have suggested benefits of the flu shot can be for heart failure patients, but there have not been any randomized control trials to establish these findings.
"Although we know that influenza vaccination benefits the larger population as a whole, this study serves to clarify the risk reduction in vaccination among heart failure patients. Heart failure patients are a vulnerable population with increased susceptibility to complications of infectious diseases," noted Ajith Nair, MD, of Baylor College of Medicine in Houston, who was not involved in the study.
Of the 134,048 adults with HF in Denmark studied through nationwide registries under the universal healthcare available there, 58% died of any cause over a median follow-up of 3.7 years, and 36% died of cardiovascular related incidents over a median follow-up of 3.3 years.
Vaccination coverage varied from 16% in 2003 to 52% in 2015. Patients who died within 30 days of receiving an HF diagnosis were excluded from the study.
The findings of this large and rigorously done study should be generalizable, noted Schaffner. "Heart failure patients are similar all over the world, so we can take this one to the proverbial bank."
Modin disclosed relationships with the Danish Heart Foundation.