Influenza Vaccination Protects Against Risk of Death in Hypertensive Patients

Vaccination against influenza was significantly associated with a reduced risk of death from all-causes, cardiovascular causes, acute myocardial infarction (AMI) and stroke in hypertensive patients, according to an abstract presented at the European Society of Cardiology Congress 2019.

Investigators from Denmark tapped into their national health care database to comb through data from 9 consecutive influenza seasons from 2007 to 2016, which included more than 600,000 hypertensive patients. The study team set out to determine if influenza vaccination was linked to lower risks of death in hypertensive patients who are otherwise healthy.

“We have known for a relatively short time that influenza predisposes middle-aged and older adults to heart attacks (myocardial infarction) and stroke,” William Schaffner, MD, a professor of preventive medicine, Department of Health Policy at Vanderbilt University Medical Center, told Contagion®, though he was not involved in the study. “That’s information that has been accumulating over the last, let’s say, 8-10 years. It’s still not well known by doctors, incidentally, because this risk for heart attack and stroke can actually still be active, still be relevant, for the several weeks up to about a month or 6 weeks after you get over your acute influenza.”

The patients involved in the study had been treated with at least 2 different classes of antihypertensive medication, including beta-blockers, diuretics, calcium antagonists or renin-angiotensin system inhibitors the investigators noted. Before the start of each influenza season, the study authors assessed the exposure to influenza vaccination to measure death from all causes, from AMI or stroke, or cardiovascular death. Then, the patients were followed from December 1 to April 1 of the following year, which is the high-activity influenza period in Denmark.

During the study seasons, vaccination coverage ranged from 26% to 36%, the investigators found. They learned that 3.5% of patients died from all-causes, while 2.0% died from cardiovascular diseases and 0.6% of patients died from AMI or stroke. Patients who received influenza vaccination were associated with older age, diabetes, atrial fibrillation, lower educational level, lower income, and higher medication use, the investigators also wrote.

The study authors said that vaccination against influenza significantly lowered the risk for all-cause death, cardiovascular death, and death from AMI or stroke before adjusting for season, age, sex, comorbidities, medication, income and other variables. However, once they considered those factors, the study authors said vaccination still was associated with reduced risk for all-cause death, cardiovascular death and death from AMI or stroke.

“Once this information gets out there, I think it will come to the great attention of everyone who’s interested in immunization and public health. And indeed, cardiovascular disease,” Schaffner continued. “It really suggests that all of us ought to make influenza vaccination part of chronic disease management. This is as important as giving a patient anti-hypertensive medication. If you can give a patient an inoculation, a 1-time inoculation that during the subsequent influenza season substantially reduces the risk of stroke and heart disease? Wow, that’s really big news.”

One of the most important takeaways that Schaffner found with this study is that, as “imperfect as influenza vaccine is, it has effects such as this that are really beyond preventing the influenza illness itself… This is going to be, I think, a quite noteworthy study.”

With this research, Schaffner thinks that investigators will be increasingly looking at different populations and how they are impacted by the influenza vaccination. This was a study on hypertensive populations, but it is also important to consider underlying lung diseases and other aspects of cardiovascular disease. Studies considering those populations will help determine how generalizable the Dutch investigators’ findings are.

The abstract, The Flu Vaccine and Mortality in Hypertension. A Danish Nationwide Cohort Study, was presented at the European Society of Cardiology Congress 2019 in Paris, France in August.