Influenza Vaccines: Another Jab at Cardiovascular Disease

Gregory Weiss, MD

The influenza (flu) vaccine has been around for a very long time. Even with highly variable efficacy from year to year, the flu vaccine is routinely recommended for everyone prior to the winter months and especially for high-risk patients. Over the years clinicians began to notice that during flu epidemics, more people were dying of cardiovascular causes than during non-epidemic periods.¹

Until recently, observational studies suggested that the influenza vaccine may have a protective effect with regards to cardiovascular events. These data were subsequently supported by small, randomized trials.² While flu vaccination is currently recommended for patients with heart disease it is not the standard of care following myocardial infarction. More recently the Influenza Vaccination After Myocardial Infarction (IAMI) study was completed looking at flu vaccination after myocardial infarction (MI) or percutaneous coronary intervention (PCI) in high-risk patients. The results from this pivotal study were presented this month at the 2021 European Society of Cardiology (ESC) Congress.

The IAMI trial was the first randomized, placebo-controlled, double-blinded, multicenter trial to look at the flu vaccine in the setting of acute coronary syndromes (ACS) and MI.³ Ole Frobert, MD, PhD, of Orebro University Hospital, Sweden presented the findings at the ESC congress meeting. The results of the trial were exciting to say the least. Frobert and colleagues found that flu vaccination early after an MI or in high-risk coronary heart disease resulted in a lower risk of all-cause death, MI, or stent thrombosis, as well as a lower risk of all-cause and cardiovascular death at 12 months compared with placebo.³

“Our findings suggest that influenza vaccination should be considered as part of in-hospital treatment after myocardial infarction,” Frobert states.¹

These results are very promising. The flu vaccines have become ubiquitous across the world with a long track record of safety. With cardiovascular disease continuing to rise worldwide prevention remains a mainstay of cardiovascular medicine. However, the IAMI study suggests that vaccinating patients hospitalized with ACS within 72 hours may dramatically reduce morbidity and mortality after MI.³ Frobert and colleagues speculate that the protective effect from flu vaccination in this setting could be from anti-inflammatory effects from the vaccine and or prevention of acute influenza infection which may trigger acute coronary events.³

The authors of the study did want to point out that the study was halted during the COVID-19 global pandemic but that the results remain robust with over 2,500 patients enrolled.¹ These results underscore the importance of vaccination programs. The general public generally look at vaccines as a preventative measure when it comes to individual infections. However, the global COVID-19 pandemic has brought vaccines into specific relief these days.

Frobert and colleagues have uncovered an important secondary preventative function of a well-known flu vaccine. While this study gives hope to many cardiologists and patients a war of information currently plagues the scientific community. This fact makes organizations like the ESC more important than ever. The 2021 ESC Congress is just the vehicle we need to disseminate fact through scientific rigor and a global presence. Moving forward, cardiologists can pass this information on to their patients with confidence rooted in strong consensus and pivotal research.

The IAMI study will have a lasting impact on cardiovascular care. Frobert and colleagues hope that the following take-home points will lead to a change in the acute management of myocardial infarction ultimately saving lives:

• The flu vaccine saves lives and should be considered as part of in-hospital treatment after myocardial infarction (MI).
• All patients with cardiovascular disease should get their yearly flu shot.
• Influenza illness is linked to cardiovascular disease.
• Evidence shows that a flu shot could prevent death caused by cardiovascular disease.

Reference:

1. https://www.escardio.org/The-ESC/Press-Office/Press-releases/Flu-jab-after-heart-attack-should-become-standard-care
2. Phrommintikul A, Kuanprasert S, Wongcharoen W, et al. Influenza vaccination reduces cardiovascular events in patients with acute coronary syndrome. Eur Heart J. 2011;32:1730–1735.
3. Frøbert O, Götberg M, Erlinge D, et al. Influenza Vaccination After Myocardial Infarction: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial. Circulation 2021; Aug 30: