Unvaccinated or partially vaccinated patients infected with the Omicron variant had a 50% higher risk of developing new-onset type 2 diabetes compared with those who tested negative, according to a recent study. 

The researchers evaluated the risk of new-onset type 2 diabetes (T2D) following SARS-CoV-2 infection during periods of Delta and Omicron variant predominance in a highly vaccinated population in Singapore. In their recent JAMA Network Open study, researchers aimed to determine whether postinfectious risk of T2D persisted in the era of milder Omicron infections and widespread booster vaccination.

Using data from Singapore’s national COVID-19 registry, the National Immunization Registry, and the National Diabetes Database, the researchers constructed two matched cohorts of adults with and without a positive SARS-CoV-2 test between September 1, 2021, and December 31, 2022. Patients were excluded if they died within 30 days of the index date, had missing demographic data, a prior T2D diagnosis, or a SARS-CoV-2 infection within the prior 300 days. The primary outcome was new-onset T2D occurring between 31 and 300 days after the index test date.

Led by Liang En Wee of the National Centre for Infectious Diseases in Singapore, the researchers included included 82,212 SARS-CoV-2–positive patients and 531,855 SARS-CoV-2–negative controls during Delta predominance, and 972,610 infected and more than 1 million uninfected patients during Omicron predominance in the analysis. Overlap weighting was used to balance covariates across groups. After adjustment, standardized mean differences for all baseline characteristics were below 0.05. The overall risk of new-onset T2D was not significantly increased during either variant period: hazard ratio (HR) = 0.99 (95% confidence interval [CI] = 0.92–1.06) during Delta and HR = 1.00 (95% CI = 0.97–1.03) during Omicron.

However, subgroup analyses revealed increased risk in specific populations. During Delta predominance, Indian patients demonstrated higher postinfectious risk of T2D compared with Chinese and Malay patients. During Omicron predominance, unvaccinated or partially vaccinated patients had a significantly increased risk (HR = 1.50; 95% CI = 1.06–2.11), while fully vaccinated or boosted patients did not. Among patients who were hospitalized with COVID-19, the postinfectious T2D risk remained elevated even after excluding those treated with corticosteroids.

Compared with a historical cohort of patients hospitalized for influenza, those hospitalized for COVID-19 had a 45% higher postacute T2D risk during Delta and a 56% higher risk during Omicron. No elevated risk of new-onset T2D was observed among fully vaccinated or boosted patients following SARS-CoV-2 infection.

The researchers reported no conflicts of interest.