An international study reveals that flu vaccines greatly reduce both pneumonia and cardiovascular complications in people with heart failure. The study was conducted by researchers from McMaster University in Canada and published in The Lancet Global Health.
The large randomized controlled trial was conducted in 10 countries in Asia, Africa, and the Middle East. Heart failure patients were matched 1:1 to receive either an annual flu shot for up to 3 years or a placebo injection of saline.
A total of 5,129 patients were involved in the study, which ran from 2015 to 2021. Over half of participants (51.4%) were women, and the mean age was 57.2 years. A total of 20.7% of participants had a previous myocardial infarction, and 8.0% had had a previous stroke.
Over the course of 1 year, a flu vaccine reduced pneumonia by 40% and hospitalization by 15% in patients with heart failure. During influenza season in the fall and winter, the vaccine reduced deaths by 20% in these patients.
Most important, fewer study participants had all-cause hospitalization in the vaccine group than in the placebo group (388 participants [15.2%] vs 455 participants [17.7%]; hazard ratio [HR], 0.84 [95% confidence interval [CI], 0.74 to 0.97]), and there were fewer recurrent all-cause hospitalizations in the vaccine group than in the placebo group (557 participants [21.8%] vs 671 participants [26.1%]; HR, 0.84 [95% CI, 0.75 to 0.94]).
In a commentary on the study, authors write that an estimated 1 billion people get flu annually around the world, with 5 million of those cases severe. More than 1 in 5 patients with heart failure have a recurrent cardiovascular event during an influenza infection.
"It is underappreciated that influenza vaccine can save people from cardiovascular death," said first study author Mark Loeb, MD, in a press release.