Glycaemic control, antidiabetic medications and influenza vaccination coverage among patients with diabetes in Udine, Italy

OBJECTIVE: The objectives of this study were to estimate influenza vaccination coverage among patients with diabetes mellitus in an Italian 250 000-inhabitant area in the 2017–2018 season and to assess whether glycaemic control and pharmacological treatment were associated with the likelihood of being vaccinated. DESIGN: In this cross-sectional study, we analysed anonymous health administrative databases, linked with each other at the individual patient level through a stochastic key: diabetes mellitus registry, vaccinations, drug prescriptions and laboratory database. SETTING: The study was conducted in the catchment area of the University Hospital of Udine (‘the Udine area’), a 250 000-inhabitant area in the northeast of Italy. PARTICIPANTS: The study included all subjects included in the regional registry of patients with diabetes mellitus, living in the Udine area as of 1 October 2017. MAIN OUTCOME MEASURES: Vaccination coverage in the 2017–2018 influenza season was calculated. The association between patients’ characteristics and the likelihood of being vaccinated was assessed through multivariate log binomial regression. RESULT: 53.0% of 15 900 patients with diabetes living in the area were vaccinated. Coverage increased with age, approaching 75% at ≥85 years. Patients lacking recent glycated haemoglobin testing were less likely to be vaccinated (43.4% vaccination coverage), as were those not treated pharmacologically (44.4% vaccination coverage). Patients treated with both insulin, metformin and other antidiabetic medications were more likely to be vaccinated than those treated with metformin alone (58.1% vaccination coverage; adjusted relative risk=1.07, 95% CI 1.01 to 1.14). CONCLUSION: Influenza vaccination coverage was suboptimal in this Italian population of patients with diabetes. Strategies to improve diabetes management could in turn positively affect influenza coverage.