COVID-19 vaccines and blood glucose control: Friend or foe?

Purpose To overview the recent literature regarding the relationship between COVID-19 vaccines and glycemic control.Methods Data were extracted from text and tables of all available articles published up to September 2023 in PubMed Database describing glucose homeostasis data in subjects exposed to COVID-19 vaccines, focusing on patients with diabetes mellitus (DM).Results It is debated if the immune system impairment observed in diabetic patients makes them susceptible to lower efficacy of vaccines, but evidence suggests a possible improvement in immune response in those with good glycemic control. Despite their proven protective role lowering infection rates and disease severity, COVID-19 vaccines can result in diabetic ketoacidosis, new-onset diabetes, or episodes of hyper- or hypoglycemia.Conclusions Evidence with COVID-19 vaccines highlights the strong relationship existing between DM and immune system function. Clinicians should strive to achieve optimal glucose control before vaccination and promptly manage possible glucose homeostasis derangement following vaccine exposure.