IVVE Trial: Flu Shot Provided Seasonal CV Benefit in Heart Failure Patients and Reduced Rates of Hospitalization and Pneumonia

Heart failure patients (HF) who received an annual influenza shot had lower rates of hospitalization and pneumonia, and lower major cardiovascular events during flu season, according to a study presented at the 2022 American College of Cardiology’s Annual Scientific Session (ACC.22).

In IVVE (Randomized controlled trial of influenza vaccine in patients with heart failure to reduce adverse vascular events), researchers enrolled 5,129 adult HF patients from 10 countries in Asia and Africa where routine flu shots are uncommon. The participants were randomized to receive an annual flu shot or placebo annually for three influenza seasons.  The trial studied the first composite primary outcome of cardiovascular death, non-fatal heart attack, and non-fatal stroke, and a second primary outcome of hospitalization for heart failure.

Overall, there was no significant difference in composite primary outcomes between those who received the flu shot and those who received placebo. However, when analyzed during peak influenza seasons only, there was a significant 18% reduction in the first primary outcome in the flu shot group, favoring flu vaccination during peak influenza periods.

Moreover, secondary analysis found that there was significant reduction in pneumonia and hospitalization in the flu shot group, with the rates of pneumonia and hospitalization to be 42% lower and 15% lower, respectively.

“If you look at this data as a whole, it really speaks to the importance of vaccinating heart failure patients,” said Dr. Mark Loeb, the study’s lead author.

While the study was conducted before and during the COVID pandemic, with enrolment ending in November 2021, the researchers found no major difference in results when analyzed before or after the start of the pandemic. “It could be that most of the events have already taken place and most of the enrolment has already finished. But when we looked at the data, there was no major difference,” said Dr. Loeb.

Although it did not meet its primary endpoint, the IVVE trial demonstrates the benefit of routine flu vaccination in patients with cardiovascular disease, consistent with previous studies such as IAMI2. It also highlights the feasibility of implementing an effective routine vaccination program in countries wherein influenza vaccination rates have historically been low.

1. Loeb M. Randomized Controlled Trial of Influenza Vaccine In Patients With Heart Failure To Reduce Adverse Vascular Events. Presented at the ACC.2022; Apr2-4, Washington, DC
2. Fröbert O, Götberg M, Erlinge D, et al. Influenza Vaccination After Myocardial Infarction: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial. Circulation. 2021 Nov 2;144(18):1476-1484. doi: 10.1161/CIRCULATIONAHA.121.057042.