Flu Shot Drops CV Risk in Type 2 Diabetes

Vaccine also lowered all-cause mortality risk

Getting a flu shot could help protect against cardiovascular disease in adults with type 2 diabetes, according to a U.K. retrospective cohort study.

Compared with unvaccinated adults with type 2 diabetes, those who got the influenza vaccine were 30% less likely to be hospitalized for stroke (incidence rate ratio [IRR] 0.70; 95% CI 0.53 to 0.91) and 22% less likely to be hospitalized for heart failure (IRR 0.78; 95% CI 0.65 to 0.92), reported a research team led by Eszter Vamos, MD, PhD, of the Imperial College London.

Vaccinated adults with type 2 diabetes were also 15% less likely to be hospitalized for pneumonia or influenza (IRR 0.85; 95% CI 0.74 to 0.99) and 24% less likely to die from any cause (IRR 0.76; 95% CI 0.65 to 0.83), Vamos and colleagues reported in the Canadian Medical Association Journal.

The study also found a non-significant trend toward reduced hospitalizations for acute myocardial infarction in vaccinated adults with type 2 diabetes (IRR 0.81; 95% CI 0.62 to 1.04).

"The health burden caused by seasonal influenza in the general population is substantial and explains much of the excess winter mortality," the researchers wrote. "Influenza infection may accelerate acute thrombotic vascular events, particularly in patients with ischemic heart disease and cerebrovascular disease."

In a statement, Vamos noted that most flu deaths every year occur in people with pre-existing health conditions such as type 2 diabetes. "This study suggests the vaccine may have substantial benefits for patients with long-term conditions. Not only might it help reduce serious illness such as stroke -- and possibly heart attack -- in high-risk individuals, but it may also reduce the risk of death in the flu season."

Co-senior study author Azeem Majeed, MD, also of the Imperial College London, added: "There are few studies looking at the effectiveness of the influenza vaccine in people with diabetes. Although there have been questions surrounding the effectiveness of the flu vaccine in recent years, this research demonstrates a clear advantage for people with diabetes."

"The flu vaccine is available free to these patients from general practitioners and pharmacists, and patients with diabetes should ensure that they receive the vaccine every year."

The retrospective cohort study included 124,503 adults age 18 or older with type 2 diabetes and medical records in the Clinical Practice Research Datalink, a database of primary care medical records in England. The investigators analyzed the data for a 7-year period, from 2003-2004 to 2009-2010.

The study's main outcome measures were hospital admissions for acute myocardial infarction, stroke, heart failure, and pneumonia or influenza, as well as all-cause mortality.

Seasonal vaccine uptake in the cohort ranged from 63% in the 2008-2009 season to 69% in the 2006-2007 season. Vaccine recipients tended to be older, generally more ill, and have more coexisting conditions; however, they also tended to have lower glycated hemoglobin and cholesterol levels.

The investigators adjusted for covariates including age, sex, duration of diabetes, number of comorbid conditions, smoking status, medications, blood pressure, body-mass index, glycated hemoglobin levels, and serum cholesterol levels.

"Additional adjustment for residual confounding did not qualitatively alter the results of the conventional analyses, but attenuated the associations for acute myocardial infarction, pneumonia or influenza, and death, and strengthened the associations for stroke and heart failure," Vamos and colleagues wrote.

A limitation of the study was that it did not evaluate whether medical records on outcomes and comorbidities might be inaccurate or incomplete, the team said.

"This study has shown that people with type 2 diabetes may derive substantial benefits from current vaccines, including protection against hospital admission for some major cardiovascular outcomes. These findings underline the importance of influenza vaccination as part of comprehensive secondary prevention in this high-risk population."

The study was funded by the National Institute of Health Research. None of the researchers reported any financial relationships with industry.

• Reviewed by Henry A. Solomon, MD, FACP, FACC Clinical Associate Professor, Weill Cornell Medical College and Dorothy Caputo, MA, BSN, RN, Nurse Planner
• This activity is part of our Clinical Context curriculum in DiabetesSource Reference: Vamos EP et al "Effectiveness of the influenza vaccine in preventing admission to hospital and death in people with type 2 diabetes" CMAJ 2016; DOI: 10.1503/cmaj.151059.

This article was first published on MedPage Today and reprinted with permission from UBM Medica. Free registration is required.