COVID-19 vaccination for diabetics: antibody level comparable to healthy individuals

When the first vaccines against COVID-19 became available, there was great uncertainty – especially among people belonging to high-risk groups. A long-term study followed 150 people with diabetes through the COVID-19 vaccination regimen and produced reassuring results. The study data also underscore the importance of regular booster vaccinations for diabetics.

Biology and Medicine

November 11, 2024

Female doctor in hospital puts on a mask — Current research results show a good antibody response to the COVID-19 vaccination in people with diabetes. Regular booster vaccinations are recommended. © unsplash+

“Back then, we were often asked in the outpatient clinic whether the vaccination was effective in the presence of diabetes and whether those affected should get it,” recalls Harald Sourij, diabetologist at the Medical University of Graz. Diabetes mellitus and the associated elevated blood sugar levels impair the immune system. During the COVID-19 pandemic, people with diabetes had a particularly high risk of getting severely ill. According to studies, one in every four diabetics who were admitted to hospital suffering from COVID-19 died.

150 individuals examined in clinical project

Today, Sourij, a clinician and researcher, refers to his own study data showing that the COVID-19 vaccination does provide comparable protection against the virus for people with diabetes. In the context of the FWF-funded project “COVID-19 vaccination in people with diabetes”, Sourij's team monitored150 participants with diabetes through the first three doses of the vaccination regimen. They examined antibody response to the vaccination, blood glucose control at the time of vaccination and possible side effects such as hyperglycemia or hypoglycemia following vaccination.

Their findings showed that the antibody response after the second vaccination was comparable to that of a healthy control group. “This gave us a lot of confidence for our work in the clinic,” notes Sourij. However, the latest study data from the project shows that the antibody level in people with diabetes drops more quickly between the second and third dose. With the booster vaccination, the antibody level – and thus, presumably, also the level of protection – could be raised to a comparable level in this group. This underlines the importance of regular booster vaccinations for people with diabetes.

In the context of the project “COVID-19 vaccination in people with diabetes”, the physician Harald Sourij and his team monitored 150 participants with diabetes through the vaccination regimen during the pandemic.

Great demand for study participation

The importance of the study then and now was underscored by the great demand for places. “It usually takes quite some time to find enough people for a study. In this case, we had 150 participants within a few weeks,” says Sourij. In addition, 86 people without diabetes were monitored as a control group. Almost all participants received vaccines based on mRNA (messenger RNA), which contains the blueprint for a harmless surface protein of SARS-CoV-2, the virus that triggers COVID-19.

In the course of the vaccinations, the researchers examined the blood glucose level and the antibody response after each of the three doses. The results showed that the vaccination protection was not dependent on whether someone suffered from type 1 or type 2 diabetes and how long the disease had been present. Nor did glycemic control play a role at the time of vaccination – which can affect the function of immune cells. “This was surprising, because we had assumed the immune response to be somewhat weaker in people with diabetes and glycemic control to influence the vaccination response,” says Sourij. Only poorer kidney function (a co-morbidity in advanced diabetes) and older age were associated with poorer immunization levels.

Hardly any influence on blood sugar

A second aspect of the study was guided by the concern that the vaccination could lead to blood sugar fluctuations in diabetics. In order to test this assumption, the participants were fitted with continuous blood glucose monitors for the first vaccination dose. The monitors documented the blood glucose levels in the subcutaneous tissue at intervals of a few minutes from two days before to three days after the vaccination. The findings showed that the vaccination had no effect on blood glucose levels in most people. Only in people who had type 1 diabetes and developed local pain and fever as a result of the vaccination were there temporary slight fluctuations in blood sugar levels. But this was to be expected in such cases according to the expert.

Further publications in the pipeline

The present study data deal with the antibody response to COVID-19 vaccination. This response is conveyed by B cells, special lymphocytes of the immune system. In addition, a large number of other cells of the immune system become active during an infection or in response to vaccination.

In a second part of the project, the researchers investigate the reaction of T cells, which are both involved in the regulation of antibody formation and can directly destroy pathogens. T cells are affected by a high blood sugar level. “This could help explain why vaccination protection is retained for a shorter period of time in people with diabetes,” says Sourij. The team is working with immunologist Margarita Dominguez-Villar from Imperial College London and her research team in order to analyze the samples collected during the study in this respect. Initial results are expected for early 2025.

Personal details

Harald Sourij is a specialist in internal medicine and Professor of Interdisciplinary Metabolic Medicine at the Medical University of Graz. He heads the Outpatient Clinic for Diabetes, Lipid and Metabolic Diseases at Graz University Hospital and the Research Unit for Interdisciplinary Metabolic Medicine. The project “COVID-19 vaccination in individuals with diabetes” was funded by the Austrian Science Fund FWF with around 350,000 euros and ran from 2022 to 2024.