New research suggests that flu vaccines can help keep heart attacks and strokes at bay in people with hypertension.

Although the flu is a common illness, the burden of this condition in the United States is considerable.

According to the Centers for Disease Control and Prevention (CDC), influenza results in up to 960,000 hospitalizations and up to 79,000 deaths every year.

In the case of people with hypertension who are already at risk of cardiovascular events, the flu can strain the immune system and raise the risk of heart attacks and strokes.

Experts agree that "the single best way to protect against the flu" is to get a vaccine early each year. The flu shot triggers the formation of antibodies approximately 2 weeks after the vaccination, which protects against infection with the virus contained in the vaccine.

Now, a team of researchers led by Daniel Modin, a research associate of the University of Copenhagen, Denmark, wondered whether putting an end to the flu infection with the aid of vaccination would protect against cardiovascular problems.

Modin and colleagues presented their findings at the European Society of Cardiology (ESC) Congress 2019 together with the World Congress of Cardiology conference, which this year takes place in Paris, France.

18% lower risk of death from any cause

The team analyzed data on 608,452 people who were 18–100 years old and had hypertension. The scientists followed the participants during nine flu seasons, from 2007 through to 2016, comparing those who had a flu shot with those who had not.

Throughout the follow-up period, Modin and team looked at death from any cause, cardiovascular death, and death from a heart attack or stroke.

The researchers also examined the link between getting a flu shot before the flu season and death risk during the flu season. They accounted for potential confounders, such as age, other medical conditions, medications, and socioeconomic status.

The research revealed an association between vaccination in the flu season and an 18% reduction in relative risk of dying from all causes, 16% less relative risk of dying from a cardiovascular event, and 10% lower relative risk of dying from a heart attack and stroke.

"We show that influenza vaccination may improve cardiovascular outcomes in patients with hypertension," comments the study's first author.

"During the nine flu seasons we studied, vaccine coverage ranged from 26% to 36%, meaning that many patients with high blood pressure were not vaccinated. If you have high blood pressure, it would be worth discussing vaccination with your doctor."

"Given these results, it is my belief that all patients with high blood pressure should have an annual flu vaccination."

—Daniel Modin

He adds, "Vaccination is safe, cheap, readily available, and decreases influenza infection. On top of that, our study suggests that it could also protect against fatal heart attacks and strokes and deaths from other causes."

The researcher also explains the common link between flu and cardiovascular events, saying that the immune reaction and ensuing inflammation during the flu may shake up a person's cardiovascular health.

Modin says, "Heart attacks and strokes are caused by the rupture of atherosclerotic plaques in the arteries leading to the heart or the brain. After a rupture, a blood clot forms and cuts off the blood supply."

"It is thought that the high levels of acute inflammation induced by influenza infection reduce the stability of plaques and make them more likely to rupture."