Effects of the COVID-19 booster vaccine on glycemia and insulin resistance in people with type 1 diabetes: A prospective pilot study.

Aims: Inflammation can trigger hyperglycemia in people with type 1 diabetes (T1D). Vaccines purposefully intend to cause an acute immunogenic response, and booster vaccines may cause even more potent immunologic responses. However, the effects of vaccines on glycemic control and insulin requirements in the days immediately post-vaccination remains poorly understood. The aim of this study was to examine the changes in glycemic control and insulin usage immediately preceding and following a COVID-19 booster vaccine among adults with T1D.

Methods: In this prospective cohort study of adults with T1D, participants wore blinded Dexcom G6 Pro continuous glucose monitors for 10 days. After a baseline period, participants received a COVID-19 booster vaccine, and subsequent changes in glycemic indices were evaluated.

Results: Among the 21 enrolled participants, 38% received a Moderna and 62% Pfizer-BioNTech booster. Compared to baseline (162.9 ± 44.1 mg/dL), mean glucose was significantly increased at Day 2 (172.8 ± 47.0 mg/dL; p = 0.04) and Day 3 (173.1 ± 45.0 mg/dL; p = 0.02) post-vaccination. Insulin resistance was also increased on Day 2 (p = 0.03). There were no differences in outcome metrics between booster vaccine manufacturers.

Conclusions: These results suggest that adults with type 1 diabetes may experience transient mild glycemic elevations after receiving a COVID-19 booster vaccination. Studies examining the effects of other vaccines are warranted.