Flu vaccine soon after heart attack cuts death, CV risk
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Influenza vaccination early after MI or in high-risk CAD was associated with a 28% lower risk for all-cause death, MI or stent thrombosis at 12 months compared with placebo, according to results of the IAMI trial.
“One of the messages from this study is if you incorporate influenza vaccination as part of routine care after MI — at least during the influenza season — you will ensure high compliance and you will ensure an effect,” Ole Fröbert, MD, PhD, adjunct professor and consultant cardiologist at Orebro University Hospital in Sweden, said during a press conference at the European Society of Cardiology Congress.
The randomized, double-blind IAMI trial enrolled 2,571 adults from 30 centers across eight countries, and was conducted during four flu seasons between October 2016 and February 2020. The average age of participants was 60 years and 18% were women; none received a flu vaccine prior to enrollment. Participants received inactivated influenza vaccine or saline placebo in a 1:1 ratio, administered shortly after MI (99.7% of patients) or hospitalization for high-risk stable CAD (0.3%).
“Target enrollment was 4,400 patients, but due to the COVID-19 pandemic, the data safety monitoring board recommended termination of the trial after 2,571 patients were enrolled in April 2020,” Fröbert said.
During follow-up, the primary outcome, a composite of all-cause death, MI or stent thrombosis at 12 months, occurred in 5.3% those assigned flu vaccine and 7.2% of those assigned placebo (HR = 0.72; 95% CI, 0.52-0.99; P = .04).
In assessing the individual key secondary endpoints, the rate of all-cause death among participants in the flu vaccine group compared with placebo was 41% lower in the flu vaccine group (2.9% vs. 4.9%; HR = 0.59; 95% CI, 0.39-0.89; P = .01), as was the rate of CV death (2.7% vs. 4.5%; HR = 0.59; 95% CI, 0.39-0.9; P = .014). MI incidence did not differ between groups (HR = 0.86; 95% CI, 0.5-1.46; P = .57).
“Our findings suggest that influenza vaccination saves lives and should be considered part of in-hospital treatment after MI,” Fröbert said. “Patients with CVD should get their annual flu shot. Influenza illness is associated with CVD and a flu shot could prevent CV death and, of course, influenza.”
Fröbert noted that it is unclear how the findings would translate to vaccine administration during non-flu seasons; however, registry studies from smaller trials suggest there could be an extended, pleiotropic effect that extends throughout the year.
“The HR, despite the fact that we did not enroll the anticipated number of participants, was more or less exactly where it was prespecified in our calculations,” Fröbert said. “The effect size was also the same as seen in small, single-center randomized trials and the same effect size as seen in meta-analyses, including observational data.”
Reference:
Perspective
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Erin D. Michos, MD, MHS, FACC, FAHA, FASE, FASPC
This is an important study. How many other interventions decrease CV death by 41%?
Our previous meta-analysis, which is cited in the paper, included 240,000 patients, though mostly observational study data, suggesting patients with CVD benefitted from the flu vaccine with a 25% reduction in all-cause mortality and an 18% reduction in CV mortality. Because our data was mostly observational, we were awaiting these new data. The most impactful evidence comes from well-done randomized controlled trials like this one. Not only is this a randomized controlled trial, but here these patients received their influenza vaccines while in the hospital or within 72 hours of their MI. This was not just patients with CVD, but those at highest risk with very recent acute coronary syndromes. Because of the COVID-19 pandemic, the researchers did not meet their target sample size. Despite an early stop, this study still shows a remarkable 28% reduction in the primary outcome of major adverse CV events, a 41% reduction in CV death and a 41% reduction in all-cause death. This emphasizes the importance of vaccination and shows this strategy works for CV prevention. This should be part of post-MI care.
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Fröbert O, et al. Hot Line: IAMI. Presented at: European Society of Cardiology Congress; Aug. 27-30, 2021 (virtual meeting).
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