People with type 1 diabetes have a higher risk of dying from Covid-19. Why are they lower on CDC’s vaccine priority list?

Laura Woerner has diligently managed her type 1 diabetes since she was diagnosed at age 11. She’s remained vigilant about anything that might throw her blood sugar levels out of balance, and now, at 36, she has had two healthy pregnancies and avoided such severe complications of diabetes as limb neuropathy or eye disease.

Woerner knows what she needs to do to maintain her health. What she doesn’t know is why the nation’s leading public health authority places people like her farther down the priority list for receiving Covid-19 vaccination than people with type 2 diabetes.

As written now, the guidelines put her in with the rest of the U.S. population under age 65, despite research showing that people with type 1 diabetes are at just as high a risk of dying from Covid-19 as those with type 2, if not higher.

“I don’t feel like I’m an apples-to-apples comparison with another healthy 36-year-old because another healthy 36-year-old, if they get a stomach virus, it doesn’t wind them up in the ER, but for me, it always has,” said Woerner, who’s an AP biology teacher in Montgomery Ala., teaching remotely. “There’s a very intricate balance. There’s thousands of decisions made in a day by somebody with type 1 diabetes that could either kill them or keep them healthy.”

Guidelines from the Centers for Disease Control and Preventions released in December rank a person with type 2 diabetes as someone who “is at increased risk” of more severe illness from Covid-19. That means people with that condition will follow health care workers and people living in long-term care settings, getting their vaccines in Phase 1c of the rollout. Data behind that ranking are considered “strongest and most consistent evidence.”

People with type 1 diabetes are in Phase 2, deemed to be patients who “might be at an increased risk” for severe illness. Data behind that ranking are classified as “limited evidence.”

Type 2 diabetes is more common, affecting 90% to 95% of people with the condition. In type 2, people can’t make enough insulin to convert the glucose their bodies need for fuel, or they grow insensitive to the insulin they do make. In the 1.6 million people in the U.S. with type 1 diabetes, their insulin-producing pancreatic islet cells have been destroyed, meaning they can’t make insulin to process glucose into energy and the sugar accumulates in the blood.

The CDC’s interpretation of risk differs from the decision made by U.K. health officials to include both type 1 and type 2 diabetes in its list of conditions that pose higher risk after Covid-19 infection.

The CDC responded with a statement that reiterates the guidelines and current evidence used to write them. “This list is a living document that will be periodically updated by CDC, and it could rapidly change as the science evolves,” Kristen Nordlund of CDC’s public affairs office wrote Monday. States are free to create their own priority lists, and in Tennessee, for example, people with both types of diabetes are classified together as at higher risk than the general population.

More recent data do exist, the advocacy and research organization JDRF argued in a December letter to the CDC’s Advisory Committee on Immunization Practices, urging the inclusion of both type 1 and type 2 diabetes in the same Phase 1c category for underlying conditions that elevate risk of bad outcomes from Covid-19 infection.

A Lancet Diabetes & Endocrinology study published in August and cited by JDRF mined 61 million medical records from the National Health Service in England to conclude that the risk of dying from Covid-19 was almost three times higher for people with type 1 diabetes and almost twice as high for type 2 than for those without diabetes. In Scotland, another Lancet study said being admitted to a critical-care hospital unit or dying was more than twice as likely for type 1 diabetes patients and nearly 1.5 times more likely for type 2 diabetes patients than for people without diabetes.

In December a study conducted by Vanderbilt University and published in Diabetes Care said people with either type 1 or type 2 diabetes who fall ill with Covid-19 have a three to four times higher risk of severe illness and hospitalization compared to people without diabetes.

And reflecting the disproportionate burden of illness borne by people of color during the pandemic, a January study in the Journal of Clinical Endocrinology & Metabolism revealed racial disparities in the diabetes numbers. Black patients with type 1 diabetes and Covid-19 were almost four times more likely as white patients to develop a serious complication called diabetic ketoacidosis.

“There is new data that warrants the CDC updating the guidelines and putting both type 1 and type 2 diabetes in the category of at risk for severe illness,” Cynthia Rice, chief mission strategy officer at JDRF, told STAT. “Glucose control has been identified as a risk factor from early in the pandemic. People with high blood sugar are at high risk of severe illness with Covid-19.”

Why is glucose control so critical?

People with diabetes aren’t more likely to become infected with Covid-19, but infections of any kind — viral, bacterial, or fungal — hit people with diabetes harder. Their bodies do not process glucose as well during illness, their immune response is weaker, and their circulation is impaired. Over a lifetime, problems with too much or too little glucose inflict widespread damage in the kidney, heart, and liver, as well as around nerves. Stroke, heart attack, kidney failure, eye disease, and limb amputations can follow poor glucose control. Inflammation rises and the immune system does not perform well.

Obesity, which is more common in type 2 diabetes but can also occur in type 1, makes all these conditions worse. Obesity is one of the underlying conditions cited by the CDC as increasing risk for worse outcomes after Covid-19 infection.

Justin Gregory, a pediatric endocrinologist and one of the Vanderbilt study authors, suspects vascular endothelial cells will explain why diabetes patients are more vulnerable to Covid-19. Forming a critical barrier between the blood and the body’s tissues, the cells fine-tune the immune system and regulate factors that cause blood to clot. These cells don’t function as well in people with either type of diabetes, increasing their chances of an exaggerated inflammatory immune response, capillary leakage in the lungs, or blood clotting throughout the body.

“It appears both groups have higher risk for severe outcomes compared with people who do not have diabetes,” Gregory said about the Vanderbilt study, which explored risk but not the biology behind it. “The data so far suggest people with type 1 diabetes have similar to somewhat higher adjusted risks of adverse Covid-19 outcomes compared to people with type 2 diabetes.”

The growing body of evidence suggests the CDC’s assessment needs revision, he said. “As states transition into immunizing individuals with high-risk conditions, I think these recent data make it imperative for health policy makers to prioritize people with type 1 diabetes among other groups with high-risk conditions.”

While states make their own policies, physicians would like latitude to do the same.

Mary-Elizabeth Patti, an adult endocrinologist at Joslin Diabetes Center, has written letters for type 1 diabetes patients asking their employers to allow them to work remotely to limit potential exposure to Covid-19.

“These are tough calls to make on who should go first to get vaccine,” she said. “There should be opportunities for physicians who know their patients to say particular factors affect immunity.”

Meanwhile, Laura Woerner waits at home with her husband — who has type 2 diabetes — and their 1-year-old and 4-year-old children. She’s pursuing a second master’s degree, in biology (her first was in secondary education) and hoping to return to a classroom someday. The CDC guidelines are baffling to her.

“I understand that the evidence is overwhelming for type 2. There’s no denying that, but I’m not really sure why it’s being treated in two different categories because the outcome is the same or even worse,” she said. “Why exclude it?”

It’s not clear when a vaccine will be available to her.

“Maybe they’ll have it at CVS in a month or two and I’ll go in and they’ll say, ‘Do you have any comorbidities?’ and I’ll say, ‘Diabetes.’ I really hope the question isn’t posed, ‘Which kind?’”

 This story has been updated with a response from the CDC.