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Vaccines may reduce the risk of post-COVID-19 type 2 diabetes

I have written previously that COVID-19 infections increase the risk of type 2 diabetes, but I did not know if vaccines could reduce the risk. A preprint article has been posted that seems to indicate that COVID-19 vaccines can reduce the risk (but not eliminate it) of post-infection type 2 diabetes.

I know that many people avoid the COVID-19 vaccines because they don’t believe the disease is dangerous or only dangerous to a specific group of people. But the facts are that the disease is linked to a lot of long-term effects, like diabetes.

I want to review this newly published study and see if vaccines are actually linked to a lower risk of post-COVID-19 infection type 2 diabetes.

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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. 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.

Numerous medical treatments and lifestyle changes 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. 

We do not know how COVID-19 infections lead to type 2 diabetes, but there has been some speculation that it is associated with an auto-immune disease caused by the COVID-19 infection.

Vaccines and post-COVID-19 infection diabetes paper

In a preprint article published on 9 August 2023 on medRxiv, researchers employed a cohort study of type 2 diabetes incidence following COVID-19 diagnosis in pre-vaccination (N=15,211,471, January 2020-December 2021) along with vaccinated (N =11,822,640) and unvaccinated (N=2,851,183) cohorts during June-December 2021. All cohorts were from the UK using medical records.

Below are the researchers’ key findings:

  • Type 2 diabetes mellitus (T2DM) incidence after COVID-19 infection was 3.01X higher than before infection in weeks 1-4.
  • The risk for T2DM was 4.86X higher in unvaccinated individuals compared to the pre-vaccine group.
  • The risk for T2DM was 1.42X higher in vaccinated people compared to the pre-vaccine group.
  • In other words, the unvaccinated group had a 342% greater risk for type 2 diabetes than the vaccinated group after the COVID-19 vaccines became available.
  • Individuals who were hospitalized for COVID-19 in the pre-vaccination cohort were 21.1X more likely to develop T2DM than the non-hospitalized

The authors concluded:

…we demonstrate that COVID-19 vaccination reduces, but does not entirely ameliorate, excess diabetes incidence after COVID-19. This supports a policy of universal vaccination and suggests that other public health activities, such as enhanced diabetes screening after severe COVID-19, may be warranted, particularly in unvaccinated people.


Before I give my thoughts on the study, I need to make clear that this paper has not been peer-reviewed, as it is a preprint. I generally do not critique preprint studies, but this one was so clear that I considered it important to discuss.

The study is powerful because it was so large — it included over 30 million people across three different cohorts. That is impressive and helps find even small differences in the risk of type 2 diabetes.

I think there are two key findings for this study:

  1. Type 2 diabetes seems to be linked to COVID-19 infection, and that hospitalization greatly increases the risk.
  2. COVID-19 vaccines reduce, but do not eliminate, the risk of type 2 diabetes post-infection.

This study provides strong evidence that COVID-19 vaccinations are critical to reducing the risk of post-COVID-19 disorders, like type 2 diabetes.


Michael Simpson

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