AHA: Study Shows Flu Shots Reduce Deaths From Heart Failure

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With the medicines and treatments available today, many people live for years after receiving a diagnosis of heart failure, although it remains one of major causes of death in the United States (cite).

But, as we've discussed often in the past (see list below), influenza and other respiratory infections are known to have a greater health impact on people with certain chronic health conditions, including coronary artery disease.

NFID: Chronic Health Problems & The Flu

Eur. Resp.J.: Influenza & Pneumonia Infections Increase Risk Of Heart Attack and Stroke

NEJM: Acute Myocardial Infarction After Laboratory-Confirmed Influenza Infection

‘Tis The Cardiac Season

Int. Med. J.: Triggering Of Acute M.I. By Respiratory Infection

It follows then, that if you can reduce the incidence (or at least the  severity) of influenza infection in the general population using the flu vaccine, you ought to be able to reduce the number of deaths among high risk individuals.

Proving that, however, hasn't been easy:

• In 2010 we saw a study in the CMAJ: Flu Vaccinations Reduce Heart Attack Risk that found that those over the age of 40 who get a seasonal flu vaccine each year may reduce their risk of a heart attack by as much as 19%. Questions were raised over the way this study was conducted (see Vaccine/Heart Attack Study Questioned), and so the results are in dispute.
• In August of 2013 (see Study: Flu Vaccine May Reduce Heart Attack Risk), we looked at study out of Australia – published in the BMJ Journal Heart, that found compelling – but not exactly conclusive – evidence that flu shots may reduce the risk of heart attacks as much as 45%.
• In October of 2013 (see JAMA: Flu Vaccine and Cardiovascular Outcomes) we looked at a meta analysis that found among patients who had previously had a heart attack, the receipt of a flu vaccine was linked to a 55% reduction in having another major cardiac event in the next few months. 

Over the past couple of years, the evidence has become much clearer, and there is some evidence - that even when it doesn’t prevent infection - the flu vaccine may reduce the severity of illness (CDC: Flu Shots Reduce Hospitalizations In The Elderly). 

All reasons why - despite its moderate and sometimes inconsistent record of protecting against influenza infection - I get the flu shot every year, and recommend that others do so as well. 

Adding to the list of studies on the flu vaccine reducing coronary deaths, we have the following study appearing this week in the American Heart Association's journal Circulation, which finds a substantial reduction in deaths among heart failure patients who received a yearly flu shot.

Influenza Vaccine in Heart Failure: Cumulative Number of Vaccinations, Frequency, Timing, and Survival: A Danish Nationwide Cohort Study
Daniel Modin, Mads Emil Jørgensen, Gunnar Gislason, Jan Skov Jensen, Lars Køber, Brian Claggett, Sheila M. Hegde, Scott D. Solomon, Christian Torp-Pedersen, and Tor Biering-Sørensen
Originally published10 Dec 2018Circulation. 2018;0

Abstract

Background: Influenza infection is a serious event for patients with heart failure (HF). Little knowledge exists about the association between influenza vaccination and outcome in patients with HF. This study sought to determine whether influenza vaccination is associated with improved long-term survival in patients with newly diagnosed HF.

Methods: We performed a nationwide cohort study including all patients who were >18 years of age and diagnosed with HF in Denmark in the period of January 1, 2003, to June 1, 2015 (n=134048). We collected linked data using nationwide registries. Vaccination status, number, and frequency during follow-up were treated as time-varying covariates in time-dependent Cox regression.

Results: Follow-up was 99.8% with a median follow-up time of 3.7 years (interquartile range, 1.7-6.8 years). The vaccination coverage of the study cohort ranged from 16% to 54% during the study period. In unadjusted analysis, receiving ≥1 vaccinations during follow-up was associated with a higher risk of death. After adjustment for inclusion date, comorbidities, medications, household income, and education level, receiving ≥1 vaccinations was associated with an 18% reduced risk of death (all-cause: hazard ratio, 0.82; 95% CI, 0.81-0.84; P < 0.001; cardiovascular causes: hazard ratio, 0.82; 95% CI, 0.81-0.84; P < 0.001). Annual vaccination, vaccination early in the year (September to October), and greater cumulative number of vaccinations were associated with larger reductions in the risk of death compared with intermittent vaccination.

Conclusions: In patients with HF, influenza vaccination was associated with a reduced risk of both all-cause and cardiovascular death after extensive adjustment for confounders. Frequent vaccination and vaccination earlier in the year were associated with larger reductions in the risk of death compared with intermittent and late vaccination.

 From the accompanying press release, we get the following summary:

Regular flu shots may save heart failure patients' lives
Circulation Journal report
American Heart Association

(Excerpt)

In this study, researchers analyzed data on 134,048 patients with newly diagnosed heart failure over a 12-year period. Flu vaccination rates ranged from 16 percent in 2003 to 52 percent in 2015 with a peak of 54 percent in 2009. Among the researchers' findings:

• Flu vaccination was associated with an 18 percent reduced risk of premature death, even after accounting for other factors such as medications, other health conditions, income and education.
• Annual flu vaccination following a heart failure diagnosis was associated with a 19 percent reduction in both all-cause and cardiovascular death when compared with no vaccination.
•  Flu vaccination frequency mattered; getting a flu shot less than once per year but more than not at all was associated with a 13 percent reduced risk of all-cause death and an 8 percent reduced risk of cardiovascular death.
• Timing mattered; there was a greater reduction in cardiovascular and all-cause death when vaccination occurred earlier in the flu season during September and October versus in November and December.
  

Lead study author Daniel Modin, an investigator from the University of Copenhagen in Denmark, said that while this research only looked at patients with newly-diagnosed heart failure, the protection from a flu shot likely benefits any patient with heart failure.

(Continue . . . )

While there is an obvious need for better flu vaccines (see CIDRAP: The Need For `Game Changing’ Flu Vaccines), we've seen some significant improvements over the past few years (quadrivalent vaccines, high-dose vaccines, cell based vaccines, etc.), and most years the flu vaccine provides a moderate (40%-60%) degree of protection.

Unless and until something better comes along, getting the yearly flu shot, and practicing good flu hygiene (covering coughs, washing hands, staying home when sick, etc.) remain your best bets for avoiding the flu and its complications each winter.