The development and mass production of the seasonal flu vaccine, as well as three international trials of cardiovascular outcomes of the influenza vaccine, currently underway, may inform future efforts aimed at developing and evaluating vaccine strategies for COVID- 19, according to a cutting-edge review in the Journal of the American College of Cardiology. The article evaluates whether existing flu vaccine trial networks could offer primary and secondary prevention strategies for cardiovascular disease patients at risk for complications from COVID-19.
The World Health Organization estimates that flu kills up to 650,000 people each year worldwide, making it one of the top 10 causes of death among people of all ages, especially those with one or more comorbidities such as cardiovascular diseases. Additionally, seasonal flu epidemics have been associated with population-level increases in cardiovascular hospitalization and mortality.
For these reasons, clinical guidelines recommend that the general population receive their influenza vaccine annually to reduce the risk of influenza-like illness. High-risk individuals are the most prompted to get vaccinated.
On March 11, 2020, the WHO declared COVID-19 a pandemic, with an overall fatality rate of around 2.3%. COVID-19 patients who have or are at risk for cardiovascular disease have an increased case fatality rate, including 6% for hypertension, 7.3% for diabetes, and 10.5% for cardiovascular disease.
Research has shown that viral respiratory infections, such as seasonal influenza and COVID-19, are risk factors for cardiovascular disease. Patients with cardiovascular disease are also at increased risk of complications after viral respiratory infections, including increased morbidity, mortality, and medical care use.
Current data suggest that influenza infection and the new coronavirus share similar symptoms initially, primarily fever, cough, and shortness of breath. However, COVID-19 appears to be more contagious than the flu.
“Although COVID-19 and other respiratory virus infections are associated with acute myocardial infarction and other cardiovascular events, influenza has the best evidence for a safe vaccine option for cardiovascular risk reduction to date,” Jacob A. Udell, a cardiologist at Women’s College Hospital and the Peter Munk Heart Center at Toronto General Hospital and the University of Toronto, Canada, and corresponding author of the article.
Several observational and small, randomized studies have suggested that influenza vaccination can serve as a preventive measure against adverse cardiovascular outcomes – he adds -. However, despite international guidelines recommending influenza and pneumococcal vaccination routine for patients with cardiovascular disease, uptake is substantially insufficient and is often de-prioritized.
There are currently three international trials on cardiovascular outcomes examining the cardioprotective effects of different flu vaccine formulations. The Flu Vaccine Trial to Prevent Adverse Vascular Events is a randomized, placebo-controlled clinical trial that studies adverse cardiovascular events using the New Heart Association functional class II-IV flu vaccine. York in patients from Asia, the Middle East, and Africa.
The influenza vaccination trial after myocardial infarction is also a randomized, placebo-controlled clinical trial studying patients with ST-elevation myocardial infarction (STEMI), or without STEMI, or with the stable disease of the coronary arteries (age = 75 years) undergoing coronary angiography, collecting data from Sweden, Denmark, Norway, the Czech Republic, Scotland, Latvia, Australia, and Bangladesh.
A third clinical trial funded by the National Institutes of Health (NIH) is underway in the United States and Canada, the flu vaccine trial to effectively stop cardio-thoracic events and decompensated heart failure. The first study of its kind compares two different types of flu vaccines over several flu seasons in high-risk cardiovascular patients with a recent history of myocardial infarction or hospitalization for heart failure.
Three large ongoing influenza vaccine cardiovascular outcome trials have the opportunity to further contribute to our understanding of the underlying comorbidities in these patients that may be driving the morbidity and mortality associated with COVID-19 infection,” Udell highlights.
These cohorts may also be an opportunity to explore new infection prevention therapies beyond influenza vaccination in patients who have already volunteered to participate in a cardiovascular outcome study of the respiratory virus vaccine. As we develop new vaccines, we will also definitely know soon if vaccination is an effective, inexpensive, and widely available therapy that reduces cardiovascular risk, which can further help prevent fatal and non-fatal cardiovascular complications of COVID-19.