FROM THE CANADIAN MEDICAL ASSOCIATION JOURNAL
Individuals with type 2 diabetes should receive the seasonal influenza vaccines annually, as doing so significantly mitigates their chances of being hospitalized for – or dying from – cardiovascular complications such as stroke, heart failure, and myocardial infarction.
“Studies assessing influenza vaccine effectiveness in people with diabetes are scarce and have shown inconclusive results,” wrote Eszter P. Vamos, MD, PhD, of Imperial College London and her coauthors in a study published in the Canadian Medical Association Journal. “None of the previous studies adjusted for residual confounding, and most of them reported composite endpoints such as admission to hospital for any cause.”
The retrospective cohort study looked at adult patients with type 2 diabetes in the Clinical Practice Research Datalink, one of the largest databases of primary care records in England. Ultimately, 124,503 adults with type 2 diabetes were enrolled in the study, representing 623,591 person-years of observation that occurred over the course of the 7 years covered by the study. For this period, the dominant strains of influenza were A(H3N2) in 2003-2004, 2004-2005, 2006-2007, and 2008-2009, with A(H1N1) being dominant during the 2007-2008 and 2009-2010 seasons and strain B in 2005-2006 (CMAJ. 2016 Jul 25. doi: 10.1503/cmaj.151059 ).
Each year included was divided into four seasons: preinfluenza season (Sept. 1 through the date of influenza season starting); influenza season (date of season onset as defined by national surveillance data through 4 weeks after the determined date of season ending); postinfluenza season (from the end of influenza season through April 30); and summer season (May 1 through Aug. 31). The primary outcomes were defined as hospital admissions for acute myocardial infarction, stroke, heart failure, pneumonia or influenza, and all-cause death, comparing between those who received their seasonal influenza vaccines and those who did not.
Following adjustment to account for any possible residual confounding, individuals who received their influenza vaccines were found to have a 19% reduction in their rate of hospital admissions for acute myocardial infarction (incidence rate ratio, 0.81; 95% confidence interval, 0.62-1.04), a 30% reduction in admissions for stroke (IRR, 0.70; 95% CI, 0.53-0.91), a 22% reduction in admissions for heart failure (IRR, 0.78; 95% CI, 0.65-0.92), a 15% reduction in admissions for either pneumonia or influenza (IRR, 0.85; 95% CI, 0.74-0.99), and a 24% lower death rate than those who had not been vaccinated (IRR, 0.76; 95% CI, 0.65-0.83).
“Our study provides valuable information on the long-term average benefits of influenza vaccine in people with type 2 diabetes,” the authors concluded, adding that “These findings underline the importance of influenza vaccination as part of comprehensive secondary prevention in this high-risk population.”
The study was supported by National Institute of Health Research. Dr. Vamos and her coauthors did not report any relevant financial disclosures.
