For people with type 2 diabetes (T2D), COVID-19 infection leads to increased hospitalization rates and worse illness severity. We know that the immune response to COVID in people with T2D may be affected by higher than normal blood sugar levels before infection. This raises risk. Now, researchers from Italy are looking at the immune responses in people with T2D after getting a COVID-19 vaccine.

HbA1c before vaccination is important

In this study, researchers looked at the immune responses to the Pfizer vaccine in 1,123 adults with and without diabetes. For those with T2D, they also looked at the impact of a person’s blood sugar control on their immune response. Participants were divided into 3 groups: people without diabetes (average HbA1c of 5.2%), T2D patients with good glycemic control (average HbA1c of 6.5%), and T2D patients with poor glycemic control (average HbA1c of 8.1%).

Vaccine leads to a weaker immunity response in people with poor glycemic control

Researchers found that the COVID vaccine caused a weak immune response in T2D patients with poor glycemic control compared with the other two groups. Twenty-one days after the first vaccine dose, antibody levels and T-cell responses were lower in TD2 patients with HbA1c levels above 7% than in individuals with HbA1c levels at or below 7%. These data support the evidence that an efficient immune response in T2D patients with good glycemic control was similar to that of nondiabetic patients. This was true after vaccination as well. This suggests that poor glycemic control during the vaccination period might impair immune responses, increasing the risk of breakthrough infection.

In conclusion, high blood sugar levels at the time of vaccination worsens the immune response. However, achieving adequate glycemic control in the 21 days after vaccination improves the response. Controlling blood sugar levels should be the standard of care during pandemics.


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