Flu Vaccination for Better Diabetes Outcomes

Getting an annual flu vaccination could help lower complications associated with diabetes.  

Multiple studies have shown an association between influenza vaccination and improved long term survival in patients with HF, MI, stroke, and pneumonia. 

People with diabetes have an increased risk of complications, including but not limited to cardiovascular disease. They are also more susceptible to infections like influenza, putting them at higher risk of developing acute ischemic events secondary to influenza infection. 

The American Diabetes Association recommends annual influenza vaccination for all individuals with diabetes; however, this recommendation is based on low evidence level due to insufficient clinical trials linking the influenza vaccine’s effect with cardiovascular mortality in patients with diabetes. 

A recent study published in Diabetes Care and carried out in Denmark identified adults with diabetes during nine consecutive influenza seasons. It evaluated whether the influenza vaccine reduced any mortality caused by cardiovascular disease. 

The study included a cohort of over 241,000 adults with diabetes who have received at least one glucose-lowering agent within six months from the index date.  

Patients with a high-risk disease such as ischemic heart disease, heart failure, chronic obstructive pulmonary disease, cancer, or cerebrovascular disease were excluded, along with patients younger than 18 and older than 100 years old; this helped isolate the effect of the vaccine.   

The study population was stratified according to whether they received an influenza vaccination or not in at least one season during the study period (influenza season in Denmark from 2007 to 2016). The patients were monitored from December 1st until April 1st the following year or death.  

At inclusion, 78.9% of the patients were on oral antidiabetics only, 15.9% were on insulin only, and 6.3% were on both. 

Primary outcomes comprised all-cause death, cardiovascular death, and death from MI or stroke. Acute complications associated with diabetes were also assessed, including diabetic ketoacidosis and hospitalization due to hypoglycemia or coma. 

Throughout follow up, the incidence of composite outcome consisting of influenza or pneumonia was assessed along with the association between influenza vaccination and the risk of starting insulin therapy for patients who were not receiving insulin. 

The study used survival analysis to evaluate the association between the vaccine and the outcome; the researchers also used stratified multivariable Cox regression models stratified by season with multiple follow-up intervals for each patient. 

Patient characteristics such as comorbidities, household income, and medications were reassessed and updated on the index date of each Flu season; this helped account for season to season changes. 

The fully adjusted analyses of the study showed a statistically significant association between the vaccination and risk reduction in all-cause death (HR 0.83, 95% CI 0.78–0.88, P<0.001), cardiovascular death (HR 0.84, 95% CI 0.77–0.91, P<0.001), stroke/MI death (HR 0.85, 95% CI 0.74–0.98, P = 0.028) and hospital admission due to acute diabetic complications (HR 0.89, 95% CI 0.83–0.97, P= 0.006). 

Additionally, the study investigated the benefits of the influenza vaccine for patients with diabetes compared to those without. Patients were matched 1:1 by age and sex, then the fully adjusted association between vaccination and outcome was assessed in both groups (with and without diabetes). The vaccination was significantly associated with reduced risk of all-cause and cardiovascular death.  

This nationwide register-based study demonstrated that influenza vaccination was significantly associated with a reduced risk of all-cause and cardiovascular death. It also demonstrated an association between the flu vaccination and the reduced incidence of acute diabetes complications. 

To date, this is the most extensive study published supporting the American Diabetes Association’s recommendation of a flu vaccine to all patients with diabetes. However, we cannot overlook the fact that there are still no randomized controlled trials supporting that recommendation.   

Practice Pearls: 

• Diabetes is associated with multiple complications, including but not limited to cardiovascular events. 
• This study shows that annual influenza vaccination can reduce the risk of different complications in patients with diabetes. 
• The current ADA Guidelines recommend getting a Flu vaccine every year; however, more studies are needed to support this recommendation’s evidence. 

Daniel Modin, Brian Claggett, Lars Køber, et al. Influenza Vaccination Is Associated With Reduced Cardiovascular Mortality in Adults With Diabetes: A Nationwide Cohort Study. Diabetes Care. 2020 Jul 9;dc200229. 

Fairuz Afram, PharmD Candidate, University of Colorado, Skaggs School of Pharmacy and Pharmaceutical Sciences 

See more about diabetes and influenza.