Flu Vaccine Linked to Reduced CV Mortality in Adults With Diabetes

In a cohort study, investigators from Denmark used nationwide register data to analyze the relationship between influenza vaccinations and cardiovascular outcomes among individuals with diabetes. The findings, published in Diabetes Care, showed that the influenza vaccine was associated with a reduced risk of all-cause death, cardiovascular death, and death from acute myocardial infarction (AMI) or stroke in this population, suggesting influenza vaccination may improve outcomes in patients with diabetes.

Although both diabetes and influenza are associated with increased risk of AMI and stroke, few studies have explored the relationship between influenza vaccinations and cardiovascular outcomes in individuals with diabetes, the authors wrote.

Researchers used a modified cohort design with a season-specific approach, given that epidemiological data show that almost all influenza activity in Denmark occurs from December through March. Data were collected from all influenza seasons (December 1 through April 1) between 2007 and 2016.

As patients with diabetes were identified as “individuals who had filled at least one prescription for glucose-lowering medication (oral or insulin) in the 6 months leading up to each season,” investigators were not able to distinguish between type 1 diabetes and type 2 diabetes. In addition, influenza vaccination has been proven to be beneficial in patients with high-risk health conditions such as lung disease, heart disease, and cancer. Individuals with these conditions were thus excluded from the study cohort.

For each season (n = 9), patients were considered vaccinated if they had received an immunization within the 4 months before December 1. Patients were also matched (1:1) by age and sex to individuals without diabetes to investigate whether vaccination may be more beneficial for individuals with diabetes.

In total, 241,551 individuals were monitored for a median of 4 seasons (interquartile range, 2-8 seasons) for a total of 425,318 person-years. All patients were between the ages 18 and 100 years. Vaccine coverage during study seasons ranged from 24% to 36%. During follow-up, 8207 patients died of all causes (3.4%), 4127 patients died of cardiovascular causes (1.7%), and 1439 patients died of AMI/stroke (0.6%). A further 5755 (2.4%) of patients were admitted to the hospital for acute diabetes complications, whereas 7764 (3.2%) were hospitalized for influenza or pneumonia.

After adjusting for confounders, analyses revealed influenza vaccinations were associated with:

• reduced risks of all-cause death (hazard ratio, 0.83; 95% CI, 0.78-0.88, P < .001)
• reduced risks of cardiovascular death (HR, 0.84; 95% CI, 0.77-0.91, P < .001)
• reduced risks of death from AMI or stroke (HR, 0.85; 95% CI, 0.74-0.98, P < .028)
• a reduced risk of being admitted to hospital with acute complications associated with diabetes (diabetic ketoacidosis, hypoglycemia, or coma) (HR, 0.89; 95% CI, 0.83-0.97, P <.006)
• reduced risk of hospitalization for influenza or pneumonia during follow-up (HR, 0.94; 95% CI, 0.88-0.99, P <.033)

Fully adjusted models also found the association was not modified by age, and in patients without diabetes matched with patients with diabetes, vaccination was significantly associated with reduced risks of all-cause death (HR, 0.81; 95% CI, 0.74-0.90, P < .001) and cardiovascular death (HR, 0.77; 95% CI, 0.66-0.90, P < .001). Data also showed patients who underwent vaccination were older; had lower income, lower educational level, and more comorbidity; and used more medication than those who did not get vaccinated.

Due to increased risks of complications from influenza infection, the American Diabetes Association recommends individuals with diabetes to be vaccinated. “Yet, no randomized controlled trials assessing the effect of influenza vaccination in patients with diabetes exist,” researchers wrote.

Because the current study was not randomized, conclusions regarding causality cannot be drawn.

Reference

Modin D, Claggett B, Køber L, et al. Influenza vaccine is associated with reduced cardiovascular mortality in adults with diabetes: a nationwide cohort study. Diabetes Care. Published online July 9, 2020. doi:10.2337/dc20-0229