A new study shows that people with high blood pressure (hypertension) who are vaccinated against influenza have a reduced risk of dying from cardiovascular disease. Several studies suggest that flu vaccination may protect the heart and that society could reap health benefits by offering older people and those with cardiovascular disease free vaccination before the flu season begins.
A new registry study of more than 600,000 people in Denmark concludes that giving a flu jab to people with hypertension may protect their hearts, since the flu vaccine is associated with a 16% lower risk of dying from cardiovascular disease compared with unvaccinated people.
According to a researcher behind the study, the results call for further investigation of this association to determine whether people with hypertension should be offered a free flu jab.
“In Denmark, people older than 65 years and people with heart failure and other chronic diseases are offered a free annual flu jab but not people with hypertension. This should perhaps be changed if further studies confirm our finding that a flu vaccination may protect the heart,” explains Tor Biering-Sørensen, Professor, University of Copenhagen and Head of Cardiovascular Non-Invasive Imaging Research Laboratory, Herlev & Gentofte Hospital.
The research has been published in the Journal of the American Heart Association.
Vaccination protects the hearts of people with heart failure and diabetes
The researchers used Denmark’s comprehensive health registries to determine whether influenza vaccination is associated with the risk of dying from cardiovascular disease among people with hypertension.
The researchers already conducted two similar studies among people with heart failure and diabetes, and both showed that being vaccinated against influenza is associated with a reduced risk of cardiovascular death.
The researchers obtained data from the Danish National Patient Registry, the Danish National Prescription Registry and the Danish National Cause of Death Registry to find people who had been diagnosed with hypertension during nine consecutive flu seasons from 2007 to 2016.
The researchers excluded people who were younger than 18 years or older than 100 years and people who had ischaemic heart disease, heart failure, chronic obstructive lung disease, cancer or cerebrovascular disease.
Then the researchers evaluated each year whether these individuals had been vaccinated against influenza or not in that flu season.
Vaccination appears to protect against more than the flu
The researchers obtained data for 608,452 people and followed them for 5 years after each flu season, during which 26–36% of them were vaccinated.
During the follow-up period, 21,571 people died: 12,270 from cardiovascular disease and 3,846 from a stroke or heart attack.
The researchers analysed the data and adjusted for various factors and found that being vaccinated against influenza was associated with a significant reduction in the risk of dying.
· The risk of dying generally declined by 18%.
· The risk of dying from cardiovascular disease declined by 16%.
· The risk of dying from a stroke or heart attack declined by 10%.
“Even people who solely have hypertension have an increased risk of dying from cardiovascular disease if they have not received a flu jab. The increased mortality is lower than what we found among people with heart failure and diabetes, but vaccination in this population is still associated with a reduced risk,” says Tor Biering-Sørensen.
Major study will confirm the results
Tor Biering-Sørensen explains that this study alone is insufficient to conclude that vaccination definitely protects the heart. People who get a flu jab might just generally be more aware of their health and have healthier lifestyles. He therefore advocates a major randomised controlled trial in which many thousands of people with hypertension are either vaccinated or not.
Then researchers can investigate whether the vaccine itself provides direct cardiovascular protection, with the mechanisms currently being unclear.
“Our result is a hypothesis-generating result that can be examined in a trial, which we are also planning. Only when we obtain the results of a major randomised controlled trial can we make definite recommendations to health authorities on who should and who should not be offered a flu jab free of charge to reduce the risk of dying from both the flu and cardiovascular disease,” concludes Tor Biering-Sørensen.
