As the flu season is fast approaching, a timely study links receiving a flu vaccination with a lower risk of serious cardiovascular events, including heart failure or heart attack. And researchers say patients who have experienced recent acute coronary syndrome see the greatest effect.

Authors from the study, recently published in JAMA, say that previous research has suggested a “strong inverse relationship” between the flu vaccine and the risk of cardiovascular events.

“Among nontraditional cardiovascular risk factors,” the authors say, “there remains interest in a potential association between respiratory tract infections, of which influenza and influenza-like illnesses are common causes, and subsequent cardiovascular events.”

To determine whether a flu shot can help prevent cardiovascular events, Dr. Jacob A. Udell, of the University of Toronto, and colleagues analyzed all randomized clinical trials of the flu vaccine that studied cardiovascular events as safety outcomes.

They found five published randomized trials and one unpublished one, resulting in a total of 6,735 patients who met criteria for the study. The average age of the participants was 67 years. Women comprised 51% of the patients, and 36% of the participants had a cardiac history.

In the five published trials, within 1 year of follow-up, only 95 of the 3,238 patients (2.9%) given the flu vaccine experienced a major adverse cardiovascular event, compared with 151 of 3,231 patients (4.7%) given a placebo or control.

The information in the unpublished trial closely matched the published data, with 2.9% in the flu vaccine group and 4.6% in the control group experiencing cardiovascular events.

After analyzing a subgroup of patients from the published data who had pre-existing coronary artery disease (CAD), the researchers found that patients who had a recent history of acute coronary syndrome (ACS) had an especially lowered risk of major adverse cardiovascular events.

Of patients in the group that received the vaccine, 10.3% experienced adverse cardiovascular events, compared with 23.1% from the placebo group.

And the researchers say results were similar in the unpublished data.

The authors conclude the study by reflecting on future endeavors:

Future research with an adequately powered multi-center trial to confirm the efficacy of this low-cost, annual, safe, easily administered and well-tolerated therapy to reduce cardiovascular risk beyond current therapies is warranted.”

In an accompanying editorial, Dr. Kathleen M. Neuzil, of PATH, Seattle, says that there are several ways to increase vaccination coverage. Some of these include:

  • Expanding access through nontraditional settings, such as the pharmacy, workplace or school
  • Improving use of evidence-based practices at medical sites, and
  • Utilizing immunization registries.

Dr. Neuzil writes:

One of the most consistent and relevant findings of operational research is that recommendation for vaccination from physicians and other health care professionals is a strong predictor of vaccine acceptance and receipt among patients.

While few are in a position to develop new influenza vaccines, all health care practitioners can recommend influenza vaccine to their patients.”

Though not everyone decides to get the shot each year, health officials recently reported that flu vaccine coverage is on the rise in the US.