The guidelines in high-income countries call for all individuals with diabetes to receive influenza vaccinations, but there is lack of evidence to back this policy. However, a new study in Diabetologia (the journal of the European Association for the Study of Diabetes) suggests that working age adults with diabetes are at an increased risk of influenza compared with people without diabetes, affirming the need to target people with diabetes for influenza vaccination. The study is by the team led by Dr Jeffrey A. Johnson, School of Public Health, University of Alberta, Edmonton, AB, Canada.
The American Diabetes Association and the Canadian Diabetes Association, as well as national vaccination authorities in Canada and the UK, 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 (age > 65 years) adults, the additional effect of guidelines calling for vaccinations in diabetic adults is to add working age (age ≥18 and <65 years) adults with diabetes as a high-risk group relative to those without diabetes.
The authors discuss 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 used data from Manitoba, Canada, from 2000 to 2008. All working age adults with diabetes were identified and matched with up to two non-diabetic controls. The rates of physician visits and hospitalisations for influenza-like illness, hospitalisations for pneumonia and influenza, and all-cause hospitalisations were analysed. The study included 163,202 people, mean age 52.5 years, of whom just under half (48.5%) were women. The data showed that adults with diabetes had more co-morbidities 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 hospitalisations associated with influenza compared to adults without diabetes. This translates to a total additional burden of 54 hospitalisations across Manitoba in working age adults due to their diabetes. No statistically significant differences were detected in influenza-attributable rates of the other outcomes, i.e.: influenza-like illness or pneumonia and influenza.
The authors say that the even if vaccination effectiveness were as low as 20%, it could be cost-effective to vaccinate adults with diabetes to avoid the costs of hospitalisation with influenza. However they add that the individual situation in different countries could vary depending on local practices and costs.
The authors say: "Our observation that working age adults with diabetes experience a greater burden of influenza than similar non-diabetic adults provides a clinical justification for targeted anti-influenza interventions; identifying particular interventions and evaluating their effectiveness in this population are questions for further research."
They conclude: "Vaccination guidelines indirectly single out working age adults with diabetes for routine vaccination. We have demonstrated an increased burden of influenza in this population. Randomised trials are needed to confirm actual vaccination effectiveness in this group. Formal economic studies are also required, to ascertain the extent to which identifying diabetes as a high-risk indication for vaccination may mitigate the use of healthcare resources and costs associated with influenza. Until such studies are available, our work represents the strongest current evidence highlighting the burden of influenza, and the potential benefits of influenza vaccination, in diabetic adults."