Does COVID Vaccine Blunt Elevated Diabetes Risk After Infection?

New evidence further supports the link between COVID-19 infection and new-onset diabetes, but also suggests that vaccination may mostly mitigate this risk, researchers reported.

In a cohort of nearly 24,000 adults at a large California health system, adjusted models showed that having a history of a treated COVID infection was tied with a 58% higher likelihood of developing new-onset diabetes compared with a new diagnosis of a benchmark condition (OR 1.58, 95% CI 1.24-2.02, P<0.001), according to Alan Kwan, MD, MSc, of Cedars-Sinai Health System in Los Angeles, and colleagues.

However, this risk appeared to be mostly driven by unvaccinated individuals, the group detailed in JAMA Network Open.

Unvaccinated individuals saw a 78% increased chance of developing diabetes within 90 days of infection (OR 1.78, 95% CI 1.35-2.37, P<0.001), while no significant association was observed in vaccinated individuals (OR 1.07, 95% CI 0.64-1.77).

Kwan's group noted, however, that although the diabetes risk was higher among the unvaccinated individuals, "suggesting a benefit of vaccination," the interaction term between vaccination status and diabetes diagnosis didn't reach statistical significance (OR 0.59, 95% CI 0.34-1.06, P=0.08). No interaction was observed for age, sex, or preexisting cardiovascular risk factors, including hypertension or hyperlipidemia.

"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," said Kwan in a statement. "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," he added.

To account for temporal confounders stemming from disruptions in healthcare use during the pandemic, the researchers used a new benchmark diagnosis -- such as urinary tract infection and gastroesophageal reflux -- as the comparator to represent a marker of healthcare engagement unrelated to COVID-19. Models were adjusted for sex, timing of index infection, and pre-infection vaccination status.

COVID-19 infection didn't appear to increase the risk for other cardiometabolic conditions compared with a benchmark diagnosis, however, specifically in regards to new-onset hypertension (OR 1.06, 95% CI 0.88-1.28) and hyperlipidemia (OR 0.91, 95% CI 0.73-1.15), the team said.

"Mechanisms contributing to postinfection diabetes risk remain unclear, although persistent inflammation contributing to insulin resistance is a proposed pathway," the researchers explained. "Our results suggest that this risk persisted as the Omicron variant became predominant, and the association remained even after accounting for temporal confounders."

This wasn't the first study to draw a line between COVID and diabetes risk either. Kwan's group referred to a meta-analysis published in November 2022 that found a 48-70% higher relative risk of type 1 and type 2 diabetes in people with a history of COVID. One of the studies included in this meta-analysis found that people who survived the post-acute phase of a COVID-19 infection (i.e., the first 30 days) had an 85% higher risk of needing a new antihyperglycemic medication.

The current 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 average age was 47 years and diagnostic data were pulled from ICD-9 and ICD-10 codes. A total of 14,856 patients were unvaccinated prior to infection and 8,853 were vaccinated.

During the study time frame, incidence of new-onset type 2 diabetes was 2.1% overall: 2.7% of the unvaccinated group and 1% of the vaccinated group.

Kwan and co-authors suggested that future studies are needed "to understand cardiometabolic sequelae of COVID-19 and whether COVID-19 vaccination attenuates risk of cardiometabolic disease."

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