Neither diabetes per se nor hyperglycemia appear to impair the antibody response to SARS-CoV-2, suggesting that a COVID-19 vaccine would be just as effective in people with diabetes as in those without, new research finds.
Results from a study involving 480 patients with confirmed COVID-19 seen at an Italian hospital between February 25 and April 19 were published online October 8 in Diabetologia by Vito Lampasona, MD, and colleagues.
Antibody responses against multiple SARS-CoV-2 antigens among the 27% of patients with COVID-19 and diabetes (preexisting and newly diagnosed) were similar with regard to timing, titers, and classes to those of patients with COVID-19 and without diabetes, and the results did not differ by glucose levels.
Moreover, positivity for immunoglobulin G (IgG) against the SARS-CoV-2 spike receptor-binding domain (RBD) was associated with improved survival regardless of diabetes status.
And as previously shown, high blood glucose levels were strongly associated with greater COVID-19 mortality even in those without diabetes.
This is the first study of the immunologic humoral response against SARS-CoV-2 in patients with hyperglycemia, the authors say.
“The immunological response to a future SARS-CoV-2 vaccine will be assessed when the vaccine becomes available. However, our data allow a cautious optimism regarding effective immunization in individuals with diabetes, as well as in the general population,” wrote Dr. Lampasona of San Raffaele Diabetes Research Institute, IRCCS Ospedale San Raffaele in Milan, and colleagues.
Diabetes and hyperglycemia worsen COVID-19 outcomes
The investigators analyzed the presence of three types of antibody to multiple SARS-CoV-2 antigens in 509 participants: IgG, which is evidence of past infection; IgM, which indicates more recent or current infection; and IgA, which is involved in the mucosal immune response, for example, in the nose where the virus enters the body.
Overall, 452 (88.8%) patients were hospitalized, 79 (15.5%) patients were admitted to intensive care, and 93 (18.3%) patients died during follow-up.
Of the 139 patients with diabetes, 90 (17.7% of the study cohort) already had a diagnosis of diabetes, and 49 (9.6%) were newly diagnosed.
Those with diabetes were older, had a higher body mass index (BMI), and were more likely to have cardiovascular comorbidities, hypertension, and chronic kidney disease. As has been previously reported for diabetes and COVID-19, diabetes was also associated with increased levels of inflammatory biomarkers, hypercoagulopathy, leukocytosis, and neutrophilia.
In multivariate analysis, diabetes status (hazard ratio, 2.32; P = .001), mean fasting plasma glucose (P < .001), and glucose variability (P = .002) were all independently associated with increased mortality and ICU admission. And fasting plasma glucose was associated with increased mortality risk even among those without diabetes (P < .001).
Antibody response similar in patients with and without diabetes
The humoral response against SARS-CoV-2 in patients with diabetes was present and superimposable in terms of timing and antibody titers to that of patients without diabetes, with marginal differences, and was not influenced by glucose levels.
After adjustment for sex, age, and diabetes status and stratification by symptom duration at time of sampling, the development of SARS-CoV-2 RBD IgG antibodies was associated with improved survival, with an HR for time to death of 0.4 (P = .002).
“Of the measured antibody responses, positivity for IgG against the SARS-CoV-2 spike RBD was predictive of survival rate, both in the presence or absence of diabetes,” the authors stressed, with similar HRs for those with diabetes (0.37; P = .013) and without diabetes (0.43; P = .038).
These data confirm “the relevance for patient survival rate of the specific antigen response against spike RBD even in the presence of diabetes, and it underlines how the mechanism explaining the worse clinical outcome in patients with diabetes is unrelated to the antibody response,” they explain.
They added, “This, together with evidence that increased blood glucose levels do predict a poor prognosis even in nondiabetic individuals and the association with increased levels of inflammatory biomarkers and hypercoagulopathy, as well as leukocytosis and neutrophilia, support the speculation that glucose per se could be an independent biological negative factor, acting as a direct regulator of innate immunity.”
“The observed increased severity and mortality risk of COVID-19 pneumonia in patients with hyperglycemia was not the result of an impaired humoral response against SARS-CoV-2.”
“RBD IgG positivity was associated with a remarkable protective effect, allowing for a cautious optimism about the efficacy of future vaccines against SARS-COV-2 in people with diabetes,” they reiterated.
The authors have reported no relevant financial relationships.