COVID-19 Vaccinations, SARS-CoV-2 Infections, and Type 1 Diabetes in Finnish Children

We assessed whether 1) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination is associated with the risk of type 1 diabetes and 2) SARS-CoV-2 vaccination or infection is associated with disease severity at type 1 diabetes diagnosis.

Every Finnish child aged 5-14 years diagnosed with type 1 diabetes (case subjects, n = 433) during a 16-month period (September 2021 to December 2022) were compared with three control subjects matched for age, sex, and municipality. Information on coronavirus disease 2019 (COVID-19) vaccinations was obtained from the National Vaccination Register. SARS-CoV-2 infections were identified based on circulating antibody titer in samples obtained soon after the diagnosis of type 1 diabetes.

COVID-19 vaccinations preceding type 1 diabetes diagnosis were not associated with risk of type 1 diabetes (hazard ratio 1.30, 95% CI 0.97-1.72, P = 0.076). Vaccinations were linked to less severe symptoms at the time of diagnosis. Children with protective HLA genotypes were more common among the vaccinated case subjects compared with unvaccinated case subjects. Vaccinations were inversely associated with insulin autoantibody positivity. There was no association between SARS-CoV-2 and type 1 diabetes symptoms or autoantibodies at the time of type 1 diabetes diagnosis.

There was no significant association between SARS-CoV-2 vaccination and risk of type 1 diabetes. Neither COVID-19 vaccinations nor SARS-CoV-2 infections explain the more severe symptoms at type 1 diabetes diagnosis observed in Finnish children after the beginning of the COVID-19 pandemic. Parents who vaccinate their children are more likely to seek medical care. This may result in less severe symptoms in their children at diagnosis of diabetes.