COVID-19 Vaccine Does Not Affect Glycemic Control in People With Diabetes

Nurse uses glaucometer to check a female patient’s blood sugar leve.
The COVID-19 vaccine is particularly recommended for people with chronic conditions like type 1 and type 2 diabetes. Researchers sought to find out if the vaccine caused a change in glycemic control.

COVID-19 vaccination does not significantly change glycemic control in patients with type 1 diabetes (T1D) and type 2 diabetes (T2D), according to a study in Diabetes Care, but a deterioration of glycemia was seen in people with T1D in conjunction with vaccine side effects.

The findings are based on a substudy of the multicenter, prospective Immune Response to COVID-19 Vaccination in People with Diabetes Mellitus (COVAC-DM) study. Participants were enrolled from April 2021 to June 2021. The cohort included 74 patients with diabetes who had sufficient continuous glucose monitoring (CGM) data available during their first COVID-19 vaccination.

Of the cohort, 58 participants had T1D (mean age, 39.5±14.1 years; mean glycated hemoglobin [HbA1c] 57±12 mol/mol), and 16 had T2D (mean age, 60.6±6.2 years; mean HbA1c, 63±11 mmol/mol).

The majority of participants received an mRNA-based vaccine (87% BioNTech Pfizer and 6% Moderna vs 7% AstraZeneca). Data from CGM were analyzed from 2 days prior until 3 days after the first vaccination dose for time spent in different glycemic ranges.

The study authors also created a score to assess time spent in glycemic ranges in relation to side effects such as headache, body ache, fatigue, and any injection site reaction, as well as elevated body temperature of >37°C.

No significant differences were found in patients with T1D (P = .962) or those with T2D (P = .704) regarding the time in range (TIR) (70-180 mg/dL) from 2 days before receiving the vaccine until 3 days afterward. The time below range (TBR) (˂70 mg/dL; T1D, P = .952; T2D, P = .704) and the time above range (TAR) (˃180 mg/dL; T1D, P = .941; T2D, P = .715) did not change around the time of the COVID-19 vaccination.

Patients with T1D had significantly less TIR on days they experienced side effects from the vaccine, compared with days they did not experience side effects (P = .033). Side effects had no significant influence on TBR in patients with T1D (P = .925). For patients with T2D, the side effect score had no effect on TIR, TAR, or TBR.

Glycemic variability, measured as a coefficient of variation, was not significantly different regarding side effect score for either T1D (P = .206) or T2D (P = .501).

Study limitations included the small sample size of CGM data in patients with T2D. In addition, all but 1 participant of the substudy were receiving continuous subcutaneous insulin infusion (CSII) or multiple daily insulin injections (MDI), and the effect in patients with T2D treated with oral glucose-lowering agents or diet only could not be assessed.

“Of note, on days on which side effects were present, a deterioration of glycemia was observed in people with type 1 diabetes,” stated the researchers. “While this observation should be further investigated in larger studies, it can be considered when health care professionals inform their patients about potential glycemic aberrations in response to COVID-19 immunization.”

Disclosure: Some of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Aberer F, Moser O, Aziz F, et al. Impact of COVID-19 vaccination on glycemia in individuals with type 1 and type 2 diabetes: substudy of the COVAC-DM study. Diabetes Care. Published online November 30, 2021. doi:10.2337/dc21-1563

This article originally appeared on Endocrinology Advisor