Hyperglycemia Post-Influenza Vaccine in Patients With Diabetes

Background: There are more than 350 reports of hyperglycemia post-influenza vaccine according to the Vaccine Adverse Effect Reporting System. Only one case report has been published detailing unusual post-vaccination hyperglycemia. The mechanism as to why hyperglycemia may occur post-vaccination has not been fully elucidated. Objective: Primary: To identify hyperglycemia within the first 24 hours of influenza vaccine. Secondary: To identify transient property of hyperglycemia within 4 days after vaccine. Methods: Multicenter prospective cohort study. Recruitment conducted throughout San Antonio, Texas, during 2018-2020 influenza seasons. Patients were included if 18 years or older, had diabetes mellitus, and currently checking their blood glucose daily. Patients excluded if they had a recent medication change that would effect their blood glucose readings. Patients had hemoglobin A1c and blood glucose measured prior to vaccination with a single dose (0.5 mL) of the tri-valent influenza vaccine intramuscularly. Glucose readings were collected within 24 hours post-vaccination and subsequent mornings for 4 days. Results: A total of 34 patients were included. Average patient age was 75 years with 60% white, 30% black, and 10% Hispanic. Median fasting glucose pre-vaccination was significantly lower than the median value 0 to 24 hours post-vaccination (140 vs 203 mg/dL, P < 0.0001). Conclusion and Relevance: Hyperglycemia was noted 0 to 24 hours post-vaccination and was transient in nature with a return to baseline by post-vaccination day 2. This trial was conducted to close a potential gap in counseling regarding the flu vaccine and decrease any potential concern surrounding the vaccine in patients with diabetes that could lead to reduced vaccination rates.