The Incidence of Graves' Hyperthyroidism Before and After COVID-19 Messenger RNA Vaccination

Case reports of postvaccine early-onset Graves' hyperthyroidism (PVGD) after the administration of COVID-19 vaccination have emerged. Our aim was to investigate whether the incidence of Graves' hyperthyroidism (GD) has increased after the introduction of COVID-19 vaccination.

We compared the incidence of new-onset GD at a single academic center during 2 periods: December 2017 to October 2019 and December 2020 to October 2022, ie, before and after the implementation of COVID-19 vaccinations. We defined PVGD as laboratory-confirmed hyperthyroidism and GD within 4 weeks after the vaccination or clear onset of symptoms of thyrotoxicosis within 4 weeks of vaccination with evidence of hyperthyroidism and GD within 3 months.

During the prevaccination period, 803 patients carried diagnoses of GD, and of these, 131 were new. During the postvaccination period, 901 patients carried diagnoses of GD, and of these, 138 were new. There was no statistically significant difference in the incidence of GD (P = .52), age at onset, gender, or race between the 2 groups. Twenty-four of 138 newly diagnosed patients in the post-COVID-19 group met the criteria for PVGD. The median free T4 was higher, but this was not statistically significant (3.9 vs 2.5 ng/dL, P = .05). There were no differences in age, gender, race, antibody titers, or type of vaccination between PVGD and controls.

There was no increase in new-onset GD after COVID-19 vaccination. Median free T4 was higher in patients with PVGD, but this was not statistically significant.