Transient Hyperglycemia in a Patient With Type 2 Diabetes After COVID-19 Messenger RNA Vaccination: A Case Report

The development of new vaccines against the SARS-CoV-2 virus in response to the COVID-19 pandemic represents a milestone in the history of public health. However, due to the rapid development and short duration of these new vaccines, the full spectrum of side effects is not yet known. A 76-year-old man presented to the clinic for follow-up after being discharged from the emergency department for hyperglycemia. His medical history included well-controlled type 2 diabetes for two years, hypertension, and hyperlipidemia. He had recently noticed high home blood glucose readings over 400 mg/dL, and his hemoglobin A1c (mean 90-day glucose level) had increased from 6.5% to 12.6%. Notably, the patient reported having excellent health behaviors, including daily exercise, a closely monitored healthy diet, and regular blood glucose testing. After extensive endocrinology workup, the rapid change in blood glucose was thought to be due to his having recently received the COVID-19 messenger RNA (mRNA) vaccine. He was started on long- and short-acting insulin and a glucagon-like peptide-1 agonist (novel injectable type 2 diabetes medication), with improvement in blood glucose. He was tapered off all medications and remains on metformin 1,000 mg twice daily after one year.Whether the new COVID-19 mRNA vaccines directly incur hyperglycemia within certain groups of patients with diabetes is not known; thus, studies exploring the relationship between vaccine antigen binding and pancreatic function are needed.