By IDSE News Staff

Vaccinating patients with heart failure (HF) or cardiovascular (CV) disease against influenza may save them from an early death by reducing cardiac complications and pneumonia, in addition to preventing serious influenza, according to new research.

Researchers from McMaster University led an international randomized, double-blind, placebo-controlled trial at 30 centers in 10 countries in Asia, the Middle East and Africa (Lancet Glob Health 2022;10[12]:E1835-E1844. doi:https://doi.org/10.1016/S2214-109X(22)00432-6).

“Importantly, we looked at low- and middle-income countries where 80% of CV disease occurs and where flu vaccination rates are low,” said the study’s lead researcher Mark Loeb, MD, MSc, a professor of pathology and molecular medicine and the Michael G. DeGroote Chair of Infectious Diseases at McMaster University, in Hamilton, Ontario. “It is under-appreciated that influenza vaccine can save people from CV death.”

Between June 2015 and November 2021, the researchers enrolled 5,129 participants and randomly assigned patients who were at least 18 years of age with HF—New York Heart Association class II, III or IV—to receive an influenza vaccine or placebo every year for up to three years.

The first co-primary end point was a first-event composite of CV death, nonfatal myocardial infarction (MI) and nonfatal stroke. The second was a recurrent-events composite of CV death, non-MI, nonfatal stroke, and hospitalization for HF. The researchers assessed outcomes in the intention-to-treat population every six months. Secondary end points for both overall and peak periods of influenza exposure included all-cause death, CV death, nonfatal MI, nonfatal stroke, all-cause hospitalization, hospitalization for HF and pneumonia.

The first co-primary end point occurred in 380 (14.8%) of the 2,560 patients assigned to the vaccine group and in 410 (16%) of the 2,569 patients in the placebo arm (hazard ratio [HR], 0.93; 95% CI, 0.81-1.07; P=0.30). The secondary end points of all-cause hospitalizations (HR, 0.84; 95% CI, 0.74-0.97; P=0.013) and pneumonia (HR, 0.58; 95% CI, 0.42-0.80; P=0.0006) were reduced significantly in the vaccine group compared with the placebo group, according to the researchers. However, they also noted that there was no significant difference between the two groups in all-cause death, CV death, nonfatal MI, nonfatal stroke and hospitalization for HF.

In a pre-specified analysis, the researchers limited their focus to periods of peak influenza circulation, and they found that the first co-primary end point and secondary end points of all-cause death, CV death and pneumonia were significantly lower in the vaccinated patients than in those who received placebo. Conversely, the researchers found no significant difference in the second co-primary end point and the secondary end point of nonfatal MI, nonfatal stroke, all-cause hospitalization and hospitalization for HF between the two groups.

Although the two co-primary end points during the entire study period were not statistically significant, the observed reduction in pneumonia, hospitalization and CV events during peak periods of influenza circulation suggests there is likely a clinical benefit in administering the influenza vaccine to patients with HF, the researchers said.

“The flu shot should be part of the standard practice in people with HF given how simple, inexpensive and safe it is,” Salim Yusuf, MD, BS, DPhil, a professor of physiology and pharmacology in the Department of Medicine at McMaster University and the executive director of the Population Health Research Institute, also in Hamilton, and a member of the study’s research team, said. “Avoiding one-sixth of deaths from heart disease and preventing hospitalizations makes it very cost–effective, and that can have an important public health and clinical impact."