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

Diabetes is associated with an increased risk of Coronavirus disease 2019 (COVID-19) vulnerability and mortality. COVID-19 vaccines significantly reduce the risks of serious COVID-19 outcomes, but the impact of COVID-19 vaccines including their effectiveness and adverse effects in patients with diabetes are not well known yet. Here, we showed that 61.1% patients with type 2 diabetes, but not healthy controls, exhibited aggravated insulin resistance towards the booster shots of the COVID-19 vaccine. Furthermore, we showed that COVID-19 vaccination once a week also impaired insulin sensitivity in healthy mice after four weeks. We further showed that metformin, a common anti-diabetic medication, improved the impaired insulin signaling induced by COVID-19 vaccination in mice. This study suggests clinical implications for the close monitoring of glycemic control in diabetic patients after receiving COVID-19 vaccines and indicates the beneficial action of metformin in counteracting insulin signaling variations induced by COVID-19 vaccination in diabetic patients.