Purpose: To determine whether influenza vaccination is associated with lower risks of death in hypertensive patients without significant cardiovascular or other chronic disease.
Methods: Using nationwide registers, we identified all patients with hypertension in Denmark during 9 consecutive influenza seasons in the period 2007-2016 who were treated with at least 2 different classes of antihypertensive medication (beta-blockers, diuretics, calcium antagonists or renin-angiotensin system inhibitors). Patients who were not 18-100 years old or had ischemic heart disease, heart failure, chronic obstructive lung disease, cancer or cerebrovascular disease were excluded. Prior to each influenza season we assessed the exposure to influenza vaccination. End-points were death from all causes, from AMI or stroke, or cardiovascular death. For each season, patients were followed from December 1 until April 1 the next year, spanning the period of high influenza activity in Denmark.
Results: A total of 608,452 Patients were followed for a median of 5 seasons (interquartile-range: 2-8 seasons), with total follow-up time of 975,902 person-years. The vaccine coverage during study seasons ranged from 26% to 36%. During follow-up, 21,571 patients died of all-causes (3.5%), 12,270 patients died of cardiovascular causes (2.0%) and 3,846 patients died of AMI/stroke (0.6%). Vaccination was associated with older age, Diabetes Mellitus, atrial fibrillation, lower educational level, lower income and higher medication use. In unadjusted analysis considering all seasons, vaccination was significantly associated with increased risk of all-cause death, cardiovascular death and death from AMI/stroke. However, following adjustment for season, age, sex, comorbidities, medications, income, education, and more, vaccination was significantly associated with reduced risks of all-cause death, cardiovascular death and death from AMI/stroke (Figure).
Conclusion: In a nationwide study spanning 9 consecutive influenza seasons including more than 600,000 hypertensive patients without significant cardiovascular disease identified through medication use, influenza vaccination was significantly associated with a reduced risk of death from all-causes, cardiovascular causes and AMI/stroke. Influenza vaccination may improve patient outcome in hypertension.