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COVID vaccine reduces the risk of post-infection diabetes

We know that one of the potential long-term effects of a COVID-19 infection is an increased risk of type 2 diabetes — new research shows that the COVID vaccine reduces that risk. This is even more reason to get the vaccine.

As usual, I’ll look at this new research, describe the data and findings, and tell you what I think of the research.

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What is type 2 diabetes?

Just for background, type 2 diabetes mellitus (or type 2 diabetes, T2DM) is a metabolic disorder that is characterized by high blood glucose with insulin resistance and relative insulin deficiency. In general, someone with T2DM produces low (or maybe even adequate) insulin levels, but various cells and organs become resistant to insulin, so cells don’t remove or store blood glucose.

Although the cause of T2DM is not completely understood, it results from a complex interaction between diet, obesity, genetics, age, and gender. Some of the causes of T2DM are under a person’s control, like diet and obesity, but many of the causal factors are not.

Because they are often confused, it’s important to note that T2DM has a completely different etiology and pathophysiology than type 1 diabetes mellitus (T1DM, once called juvenile diabetes). Type 1 diabetes results from the inability of the beta cells of the pancreas to produce insulin, as a result of an autoimmune disease. Diet and lifestyle are not related to T1DM.

There are numerous medical treatments and lifestyle changes that can moderate, or even reverse, the course of T2DM. On the other hand, there are no cures (at this time) for T1DM, and it can be a death sentence for the patient without regular daily insulin injections. Over 90-95% of diabetes in the USA is Type 2.

The consequences of both types of diabetes are almost the same. Complications of poorly managed diabetes mellitus may include cardiovascular diseasediabetic neuropathy, and diabetic retinopathy, among many other chronic conditions. 

As I have written before, there appears to be a significant link between even mild COVID-19 infections and type 2 diabetes. The mechanism of this link is unknown at this time, but it is speculated that COVID-19 infection may lead to diabetes by up-regulation of the immune system after remission, which may induce pancreatic beta-cell dysfunction and insulin resistance, or patients may have been at risk for developing diabetes due to having obesity or prediabetes, and the stress COVID-19 put on their bodies speeded it up.

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COVID-19 vaccine and type 2 diabetes

In a paper published on 1 February 2023 in JAMA Network Open, Alan C Kwan, MD, MSc, of Cedars-Sinai Health System in Los Angeles, and colleagues examined a large cohort of adults in the large California healthcare system.

The study included 23,709 adult patients (54% of whom were female) with at least one COVID-19 infection treated within the Cedars-Sinai Health System between the beginning of the pandemic through June 2022

The researchers found the following:

  • A history of a treated COVID infection had a 58% higher risk of developing new-onset type 2 diabetes compared to those who had not, with an odds ratio (OR) = 1.58.
  • Unvaccinated individuals saw a 78% increased chance of developing diabetes within 90 days of a COVID-19 infection OR = 1.78.
  • In vaccinated individuals, there was no significant association between infection and type 2 diabetes OR = 1.07.
  • During the time frame of the study, the incidence of new-onset type 2 diabetes was 2.1% overall — it was 2.7% of the unvaccinated group and approximately 1% of the vaccinated group.

The lead author of the study, Alan C Kwan stated:

Our results validate early findings revealing a risk of developing type 2 diabetes after a COVID-19 infection and indicate that this risk has, unfortunately, persisted through the Omicron era. These results suggest that COVID-19 vaccination prior to infection may provide a protective effect against diabetes risk.

Although further studies are needed to validate this hypothesis, we remain steadfast in our belief that COVID-19 vaccination remains an important tool in protecting against COVID-19 and the still-uncertain risks that people may experience during the post-infection period.

More studies linking COVID-19 to diabetes

  • This 2023 study concluded that: “COVID-19 infection has an impact on blood sugar levels and altered glycemic control, switching a few individuals into diabetic and a significant number of individuals into the pre-diabetic state, who are non-diabetic individuals before COVID-19 infection.”
  • This December 2023 study concluded that: “Our data from this 6-year study on more than 200,000 adult participants indicate that the incidence of T2D (type 2 diabetes) was significantly higher during the pandemic compared to the pre-COVID-19 phase.
  • This December 2023 study showed that vaccinated individuals with type 1 diabetes had better glucose control compared to non-vaccinated individuals.
  • This November 2023 study provided evidence that the incidence of type 1 and type 2 diabetes increased during the COVID-19 pandemic.

I could add many more studies that showed a link between COVID-19 and diabetes, especially in unvaccinated individuals, but I don’t want this article to end up being 50,000 words.

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This study from Kwan et al. provides robust data supporting two hypotheses — first, that a COVID-19 infection greatly increases the risk of type 2 diabetes, and second, that the COVID-19 vaccine reduces the risk of diabetes to the level of someone who has not been infected.

Because of the size of the population studied and the type of analysis done on the data, I give this article five out of five stars. Given the amount of research that has already shown that one of the long-term consequences of a COVID-19 infection is type 2 diabetes, I don’t think there are many doubts about a link between the two diseases. This study clearly shows that the COVID-19 vaccine mitigates the risk of type 2 diabetes.

And there are many more studies that support the conclusions of this study. It is clear that there is a link, though we don’t know why at this time.

However, it is one more reason to get the vaccine. It helps prevent diabetes.


Michael Simpson

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