Does influenza vaccination reduce deaths and vascular events in patients with heart failure?

Does influenza vaccination reduce deaths and vascular events in patients with heart failure?

In a recently published study in The Lancet Global Health Researchers conducted a placebo-controlled, double-blind clinical trial to assess whether influenza vaccination was effective in reducing vascular events and mortality in patients with heart failure.

Lernen: Influenza-Impfstoff zur Verringerung unerwünschter vaskulärer Ereignisse bei Patienten mit Herzinsuffizienz: eine multinationale randomisierte, doppelblinde, placebokontrollierte Studie. Bildnachweis: antoniodiaz/Shutterstock

background

Heart failure is a major global health problem, and the incidence of heart failure has doubled over the past three decades. In addition, influenza infections have increased the risk of cardiovascular events and death.

However, observational studies, placebo-controlled trials, and cohort studies have reported a decrease in ischemic events and all-cause mortality in patients with a history of cardiovascular disease. Given the low influenza vaccination rates and increased risk of heart failure in low- and middle-income countries, it would be helpful to understand the effectiveness of influenza vaccination in reducing the risk of cardiovascular events in patients with a history of heart failure.

About studying

In the present study, researchers conducted a randomized, placebo-controlled clinical trial at 30 sites in 10 countries in Africa, Asia, and the Middle East. The study compared the effect of influenza vaccination and a placebo on the incidence of cardiovascular events in patients with heart failure over three influenza seasons. The sites consisted of hospitals affiliated with research institutes or universities, and the heart failure patients were recruited from the hospitals or using local health databases.

Patients over 18 years of age with clinically diagnosed heart failure were recruited for the study. Participants were excluded from the study if they had contraindications to the vaccine or had received the influenza vaccine in the past three years. Patients with severe valvular heart disease requiring surgery to repair or replace heart valves were also excluded.

Participants were randomly assigned in a 1:1 ratio to the vaccine or placebo group and each received 0.5 ml of the influenza vaccine or saline administered intramuscularly. The primary endpoints included nonfatal myocardial infarction, heart failure-related hospitalizations, nonfatal stroke, and cardiovascular deaths. Secondary endpoints included all primary endpoints, all-cause death, all-cause hospitalization, and pneumonia.

Results

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Results showed a significant decrease in primary and secondary outcomes in patients in the vaccination group during the peak influenza season. However, the results were not statistically significant for the entire observation period.

A total of 5,129 patients were enrolled in the study, 2,560 of whom received the influenza vaccine and the rest the placebo. Primary endpoints such as cardiovascular death, nonfatal stroke, and myocardial infarction occurred in 380 and 410 participants in the vaccine and placebo groups, respectively. When heart failure hospitalizations were added to the results, the numbers rose to 524 and 570 for the vaccine and placebo groups, respectively. In addition, when analyzing recurrent events, the incidence of cardiovascular death, nonfatal stroke or myocardial infarction, and hospitalization for heart failure increased to 754 and 819 in the vaccine and placebo groups, respectively.

It was observed that secondary outcomes of pneumonia and all-cause hospitalizations were significantly lower in patients in the vaccine group than in those in the placebo group. However, the other secondary endpoints such as cardiovascular death, death from any cause, hospitalization for heart failure and non-fatal stroke and myocardial infarction did not show a significant decrease in either group.

However, during peak periods of influenza circulation, primary and secondary outcomes were significantly reduced in the vaccination group compared to the placebo group. In addition, events were also lower when the vaccine strain was similar to the circulating influenza strain.

The reduction in risk during the peak influenza season observed in the present study was similar to another study evaluating the effectiveness of the influenza vaccine in reducing all-cause death and myocardial infarction in patients with a history of myocardial infarction. The results also confirmed the results of the meta-analysis of other observational studies on the effect of the influenza vaccine in reducing cardiovascular events in patients with heart failure.

Conclusions

Overall, the results showed that administration of the influenza vaccine resulted in a significant decrease in cardiovascular deaths, heart failure-related hospitalizations, nonfatal stroke, and nonfatal myocardial infarction in patients with a history of heart failure during peak periods of influenza viral circulation.

Although the risk reduction was not significant for the entire observation period, the significant decrease in cardiovascular events and deaths and the significant decrease in pneumonia associated with influenza vaccination during periods of high viral circulation suggest a clinical benefit from administration of the vaccine.

Reference:

• Loeb, M. et al. (2022) „Influenza-Impfstoff zur Verringerung unerwünschter vaskulärer Ereignisse bei Patienten mit Herzinsuffizienz: eine multinationale randomisierte, doppelblinde, placebokontrollierte Studie“, The Lancet Global Health, 10(12), S. e1835-e1844. doi: 10.1016/s2214-109x(22)00432-6. https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(22)00432-6/fulltext

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