medwireNews: The proportion of on-target interstitial glucose values falls during the week following initial COVID-19 vaccination in people with type 1 diabetes, study findings indicate.
Writing in Diabetic Medicine, Adrian Heald (University of Manchester, UK) and co-authors say that the effect is “more pronounced in people talking oral hypoglycaemic medication plus insulin, and when HbA1c [glycated hemoglobin] is lower.”
Heald and team reviewed flash glucose monitoring data from 97 consecutive adults (median age 44 years, 52.5% women) with type 1 diabetes who routinely used the FreeStyle Libre system and had recently received their first dose of the Pfizer/BioNtech (46.4%) or Oxford/AstraZeneca (53.6%) COVID-19 vaccine.
The team reports that, in the 7 days before vaccination, interstitial glucose levels were within the target range of 3.9–10.0 mmol/L (70–180 mg/dL) a mean 55.0% of time.
During the 7 days after vaccination, this fell significantly to a mean 52.2% of time.
In addition, 58% of participants experienced a reduction in the proportion of readings that were on target in the week after vaccination, with 30% experiencing a decrease of more than 10%, and 10% experiencing a decrease of more than 20%.
The researchers note that there was no significant change in glucose variability following vaccination, but the proportion of readings between 10.1 and 13.9 mmol/L (182.0–250.5 mg/dL) increased by a nonsignificant 1.7 percentage points while the proportion at or above 14.0 mmol/L (252.3 mg/dL) increased by a significant 2.1 percentage points.
During the second week postvaccination, the proportion of readings in range increased slightly to 52.6%.
Subgroup analyses showed that, during the first 7 days after vaccination, the fall in interstitial glucose proportion on target was greatest among the 26 participants who were using metformin or dapagliflozin in addition to insulin, at 7.6%, which was significantly different to the 2.9% increase in readings on target observed among the 70 people on insulin only.
There was also a significant difference in the impact of vaccination between people with HbA1c levels at or below (n=49) versus above (n=48) the median of 7.3% (56 mmol/mol). Specifically, those with lower HbA1c levels experienced a 5.7% fall in readings on target during the week after vaccination whereas those with higher prevaccination levels experienced no change in the proportion on target.
Conversely, there was no significant difference in the change in proportion on target by age, sex, diabetes duration, BMI, or vaccine type.
Furthermore, Heald et al say “there was no evidence of any other factor than the vaccination to account for the changes in interstitial glucose profile–that is there was no evidence of intercurrent illness, minor operation or other events that would significantly influence interstitial glucose levels.”
The researchers therefore believe their results suggest “that patients with [type 1 diabetes] should be counselled and prepared for possible transient hyperglycaemia following the COVID-19 vaccine.”
They add that further studies are planned to investigate whether a similar effect is seen following a second COVID-19 vaccination.
medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2022 Springer Healthcare Ltd, part of the Springer Nature Group
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