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

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.

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.

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.

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.

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.

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).

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.