Flu season has returned and with it, a new round of vaccines. While this year the vaccine may not be a perfect match to the A strain, cardiologists will want to recommend the shot for their patients, regardless.

“We’ve seen in the data that for patients at high risk for cardiovascular complications, the flu vaccine offered a more than 30 percent benefit overall and that signal was amplified in patients with a recent heart attack,“ said Jacob A. Udell, MD, MPH, a cardiologist at the Women’s College Hospital and Toronto General Hospital, in an interview with Cardiovascular Business.  

In 2013, Udell and colleagues published a meta-analysis linking improvements in cardiovascular outcomes to flu shots. Their findings and others published earlier that year have become part of recommendations issued by the Canadian government and the Centers for Disease Control and Prevention (CDC) in the U.S. for this season’s flu shot. In December, 4 percent of Americans self-reported having the flu, according to the Gallup poll. The CDC estimated that 145.4 million doses of flu vaccine were administered through Dec. 5. However, this represented coverage of less than 50 percent of the general population, according to early season statistics.

Although he noted that antibody response is highly variable, even when the vaccine was a match for the seasonal flu, it still provided a reduction in cardiovascular complications and mortality among those at risk. Other flu protection strategies are being tested, including a higher dose vaccine, a booster vaccine or other formulations or other preservatives that might help make the vaccine more effective against the flu.

However, Udell said that it is possible that part of the cardioprotection may not come from protection against the virus, but from how the body responds to stress. “Some data support that the flu vaccine may turn on the bradykinin 2 receptor,” he said, which in and of itself is cardioprotective. “So maybe this is something that has nothing to do with the flu, per se, but is a pleiotropic effect of the vaccine.”

At this point, Udell noted, there is no data linking antivirals to the same improvement of cardiovascular outcomes seen with the flu vaccine.

Udell recommended cardiologists suggest flu shots to their patients even now, to benefit from the cardioprotective effect and to protect against the upcoming round of B strain. He also advised cardiologists and other healthcare professionals get vaccinated. 

“The worst offenders are healthcare workers,” he said. In response to “horrible” vaccination rates among clinicians, Canada has instituted a policy where healthcare professionals must either get the flu shot or “wear a mask for the whole flu season.” According to CDC early season data, only 64.3 percent of all U.S. healthcare practitioners were vaccinated this season.

Udell and colleagues are focusing on understanding the effect of a stronger flu vaccine dosage on cardiovascular health and getting the word out. “We’re working on a new clinical outcomes trial to drive home the point that if we can show of the benefit of more vs. standard vaccine, if we can convince healthcare payers that this is the way to go in terms of affordability and what we’re preventing, then it’s likely that that will become the new standard of care one day," he said. "We want to give the evidence to demonstrate that [it works].

“I would find it hard for the skeptics to argue with hard data that shows a reduction in major cardiovascular outcomes,” Udell said.