COVID-19 vaccination in diabetes

People with diabetes mellitus are more prone to severe episodes of COVID-19 following SARS-CoV-2 infections. Therefore, people with diabetes are considered a high priority group for COVID-19 vaccination. However, impaired immune responses are discussed in people with diabetes mellitus, which would also impact the response to a COVID-19 vaccination. In this study we aim to investigate cellular and humoral immune response following the third COVID-19 vaccination in people with type 1 and type 2 diabetes mellitus. In addition, we will investigate, if glycaemic control or other clinical parameters have an impact on the immune response in people with diabetes. Moreover, we will look into vaccine-specific T- cell responses and the role of anti-SARS-CoV-2 IgA antibodies in saliva of people with diabetes. As time is of essence in COVID-19 research, we have initiated the study already a few months ago, when we enrolled patients with type 1 and type 2 diabetes, half of them with good glycaemic control at the time of the first vaccination and the other half with glycaemic control above the currently recommended threshold. Since then, this study cohort is under regular follow up and the focus of the proposed research project is on the investigation of the response to the booster (3rd) vaccination in this patient group.

People living with diabetes were already identified at the beginning of the COVID-19 pandemic as a patient group with an increased risk of severe COVID-19 disease. With the availability of the SARS-CoV-2 vaccination, however, it was unclear whether people with diabetes would develop a reduced vaccination response, since firstly type 1 diabetes is an autoimmune disease, and secondly elevated blood sugar levels have previously been described as one cause of a reduced immune response. We therefore examined a total of 150 people with diabetes before the first SARS-CoV-2 vaccination, as well as after the first 3 vaccinations (almost all mRNA based). They belonged to one of the following four groups: 1.) People with type 1 diabetes and well controlled blood sugar, 2.) type 1 diabetes with insufficiently controlled blood sugar, 3.) type 2 diabetes with well controlled blood sugar and 4.) type 2 diabetes with insufficiently controlled blood sugar. The results were compared with those of a group of people without diabetes. It was found that the antibody response after the second vaccination was comparable in all groups, regardless of the presence of a type of diabetes or blood sugar control at the time of vaccination. Over the 6-months interval after the 2nd vaccination, there was a significantly faster decline in SARS-CoV-2-antibody titers in people with type 1 and type 2 diabetes, but the antibody response after the third vaccination was again comparable to the healthy control group. At the same time, we also investigated the influence of the SARS-CoV-2 vaccination on blood sugar levels using continuous glucose monitoring. There was no influence of the vaccination on blood sugar levels. Only people with type 1 diabetes had short-term elevated blood sugar levels on days when they had side effects (especially fever) after vaccination, as is to be expected in such situations. Our data show a good response to the SARS-CoV-2 vaccination in people with diabetes, regardless of diabetes type and blood sugar control, but antibody levels appear to decrease more quickly than in people without diabetes. Important analyses of the cellular immune response are currently still being evaluated.