People with heart failure who get flu shots may be less likely to die prematurely than their counterparts who don't get vaccinated, a Danish study suggests.
Researchers followed more than 134,000 patients with heart failure between 2003 and 2015, with half the patients staying in the study for at least 3.7 years. Overall, getting at least one flu shot was associated with an 18 percent lower risk of premature death from all causes and from cardiovascular problems in particular.
Flu shot. Source: Getty
"We also found that annual vaccination frequency and vaccination early in the season were associated with greater reductions in the risk of death," lead study author Daniel Modin of Gentofte University Hospital and the University of Copenhagen.
"We already knew that influenza vaccination benefits the population as a whole, but our study adds support to the importance of influenza vaccination in patients with heart failure, and it also suggests that annual and consistent vaccination is important in this patient group," Modin said by email.
Infections like the flu increase the body's demand for energy, requiring the heart to pump harder. Failing hearts may not be able to do this, increasing the risk of serious flu complications like pneumonia.
During the study, almost 78,000 people died from all causes, including about 48,000 who died of cardiovascular causes.
Annual flu vaccination rates ranged from a low of 16 percent in 2003 to a high of 54 percent in 2009.
People who got vaccinated every year had a lower risk of premature death than people who got vaccinated inconsistently, researchers report in Circulation, December 10.
Getting vaccinated in September or October was associated with a lower risk of premature death than getting a flu shot later in the season.
The study wasn't designed to prove whether or how vaccination might prevent premature death in heart failure patients.
Also, researchers lacked data on vaccines administered by general practitioners, so they might have undercounted the number of patients who got flu shots. They also lacked data on patient characteristics that might help explain the severity of their heart failure and influence their risk of premature death.
Even so, the results offer fresh evidence that flu shots save lives, said Dr. Jeff Kwong of the Dalla Lana School of Public Health at the University of Toronto.
People at high risk of complications from flu should get vaccinated every year, said Kwong, who wasn't involved in the study.
"We are talking about an effective, safe, and low-cost intervention," Kwong said by email. "In the northern hemisphere, getting the flu shot in November is probably the best time, due to recent concerns of waning of vaccine effectiveness over the course of an influenza season."
People without heart failure should also get vaccinated, because they'll help protect not just themselves but also people with compromised immune systems who can't get the vaccine, said Dr. Kevin Schwartz of Public Health Ontario.
"The flu shot is recommended for everyone, every year, who is over 6 months of age," Schwartz, who wasn't involved in the study, said by email. "Everyone should get a flu shot, even if you are young and healthy, in order to protect those around you who are most at risk such as babies too young to get the vaccine and those with compromised immune systems who may not respond as well to the vaccine."