The study was presented at the ‘ESC Congress 2019’ at Paris Expo Porte de Versailles in Paris, France.
“Given these results, it is my belief that all patients with high blood pressure should have an annual flu vaccination,” said Daniel Modin, first author of the study.
“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,” added Modin.
The study used Danish nationwide healthcare registers to identify 608,452 patients aged 18 to 100 years with hypertension during nine consecutive influenza seasons (2007 to 2016).
The researchers determined how many patients had received a flu vaccine prior to each season. They then followed patients over each season and tracked how many died. In particular, they recorded death from all causes, death from any cardiovascular cause, and death from heart attack or stroke.
Finally, they analysed the association between receiving a vaccine prior to flu season and the risk of death during flu season. The analysis controlled for patient characteristics that could impact the likelihood of dying such as age, comorbidities, medications, and socioeconomic status.
After adjusting for patient differences, in a given influenza season, vaccination was associated with an 18 per cent relative reduction in the risk of dying from all causes, a 16 per cent relative reduction in the risk of dying from any cardiovascular cause, and a 10 per cent relative reduction in the risk of dying from heart attack or stroke.
“We show that influenza vaccination may improve cardiovascular outcomes in patients with hypertension. During the nine flu seasons we studied, vaccine coverage ranged from 26 per cent to 36 per cent, 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,” said Modin.
Regarding how flu and cardiovascular disease might be connected, Modin noted that when the influenza virus infects the body it triggers a strong immune reaction and subsequent inflammation. These responses fight the infection and clear the virus from the body but may increase the risk of having a heart attack or stroke.