Large study supports benefits of flu vaccine for adults with diabetes

Working-age adults-aged 18 to 64-with diabetes appear to have an increased risk of being hospitalized for influenza compared to similar-aged adults without diabetes, according to a study in Diabetologia.

“This increased risk is small-6%-but nonetheless is justification for targeting adults with diabetes to get vaccinated,” according to study author Jeffrey A. Johnson, PhD, School of Public Health, University of Alberta, Edmonton, AB, Canada.​

The American Diabetes Association, the Canadian Diabetes Association, as well as national vaccination authorities in Canada and the United Kingdom, all recommend vaccinating people with diabetes against influenza.

In the United States, influenza vaccinations are recommended for all adults, although priority continues to be placed on those with diabetes. Since separate recommendations already exist for vaccination in all elderly (aged >65 years) adults, the additional effect of guidelines calling for vaccinations in diabetic adults is to add working-age (aged ≥18 and <65 years) adults with diabetes as a high-risk group relative to those without diabetes.

The researchers discussed how previous studies to assess the risk of influenza in adults with diabetes have had various methodological problems, so their aim was to do a new study to provide evidence on the recommendation to give the influenza vaccine to adults with diabetes.

The study

The study used data from Manitoba, Canada, from 2000 to 2008. All working-age adults with diabetes were identified and matched with up to two nondiabetic controls. The rates of physician visits and hospitalizations for influenza-like illness, pneumonia, and influenza-specific hospitalizations, and all-cause hospitalizations were analyzed. The study included 166,715 people, mean age 50 to 51 years, of whom just under half (48% to 49%) were women.

The data showed that adults with diabetes had more comorbidities and received influenza vaccination more often than those without diabetes. After adjusting for these differences, adults with diabetes had a 6% greater increase in all-cause hospitalizations associated with influenza compared to adults without diabetes.  This translates to a total additional burden of 54 hospitalizations across Manitoba in working-age adults because of their diabetes. No statistically significant differences were detected in influenza-attributable rates of the other outcomes, (ie, influenza-like illness or pneumonia and influenza).

Key finding

“This is one important part of the evidence-there seems to be an increased risk of getting influenza in people with diabetes,” Johnson said.  “The other part of the evidence is actually how effective the influenza vaccination is in preventing or reducing this risk.  That piece of evidence is still not clear, and was not part of this study. In fact, we emphasize there is still a need to do proper studies, specifically randomized controlled trials to determine vaccine effectiveness. The current evidence of this is very weak, with many limitations, so we actually don’t know how well these vaccinations do work.

“Nonetheless, we know there is relatively little harm-that is, there are few if any adverse effects-in getting vaccinated, so on balance, our findings provide support for the current guidelines, and for the public health message of getting an annual influenza vaccination, and especially for adults living with diabetes,” Johnson added.

Even if vaccine effectiveness were as low as 20%, it could be cost-effective to vaccinate adults with diabetes to avoid the costs of hospitalization with influenza, according to the authors. However they add that the individual situation in different countries could vary depending on local practices and costs.

For managed care organizations, this is an important message in terms of quality-of-care measures, according to Johnson. “Receipt of annual influenza immunizations is considered by some as an important measure of quality of care,” he said.