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Science Library Abstract
Published: 2024

Studies suggest the BioNTech mRNA COVID-19 vaccine impairs glucose control and aggravates insulin resistance in human subjects with type 2 diabetes.


Metformin mitigates insulin signaling variations induced by COVID-19 vaccine boosters in type 2 diabetes

L. Zhai, M. Zhuang, H. Ki Wong, C. Lin, J. Zhang, G. Bao, Y. Zhang, S. Xu, J. Luo, S. Yuan, H. Leong, X. Wong, Z. Bian

The long-term effects of COVID-19 vaccines have not been well characterized. Zhai et al. conducted a longitudinal clinical trial to determine the effects of the COVID-19 vaccine in healthy controls, pre-diabetic subjects, and diabetic subjects. The corresponding author of this study Zhaoxiang Bian, is a Professor at the Hong Kong Baptist University and a leading expert in the execution of clinical trials with Chinese medicines.

A total of 180 participants receiving BioNTech mRNA COVID-19 (BNT) vaccination (60 in each of the following groups: pre-diabetes mellitus, diabetes mellitus, and healthy controls) were recruited and observed over two weeks for their changes in insulin sensitivity before and after two doses of BNT. Biomarkers were taken for immune response, glucose intolerance, and insulin resistance. Diabetic patients exhibited similar immune responses (i.e., production of IgG antibodies) as healthy controls after receiving the BNT booster. In contrast to immune responses, authors report exacerbated risks of glucose intolerance and insulin resistance after the booster shot in pre-diabetic and diabetic patients. 61.1% and 66.7% of diabetic subjects had impairment of insulin sensitivity and increased risks of cardiovascular complications, respectively. These results suggest the vaccine impairs glucose control and aggravates insulin resistance in human subjects with type 2 diabetes. Following on, animal studies were conducted to determine the mechanisms of the inhibitory action of BNT vaccination on glucose control. Compared to mice treated with saline, mice treated with the BNT vaccine (intramuscular injection at an equivalent human dosage of 4.5 μg/kg) exhibited immune responses similar as shown by the elevation of SARS-CoV-2 spike protein in serum. After the fourth dose of BNT vaccine mice exhibited impaired glucose tolerance. Based on investigated biomarkers of diabetes the authors speculate that glucose intolerance was mediated by impairment of insulin sensitivity rather than impaired insulin secretion. Researchers further showed that metformin, a common anti-diabetic medication, improved the impaired insulin signaling induced by COVID-19 vaccination in mice.

Approximately 12% (38.4 million) and 38% (97.6 million) of the US population have diabetes and prediabetes, respectively ( Clinical and animal studies by Zhai et al. provide clear evidence of safety issues of the COVID-19 vaccines in diabetics or populations with metabolic conditions.

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