Thyroiditis After COVID-19 mRNA Vaccine: A Case Series

BACKGROUND: Although SARS-CoV-2 virus infection has been reported to cause subacute thyroiditis, the mRNA vaccine for SARS-CoV-2 is suspected to induce thyroiditis with thyrotoxicosis. CASE REPORT: : We describe 3 patients with no history of thyroid disease who presented with symptomatic, biochemical, and radiological evidence of thyroiditis with thyrotoxicosis, 10 to 20 days after receiving either Pfizer Bio-NTech or Moderna COVID-19 mRNA vaccines. All patients presented with thyrotoxicosis but with negative thyroid-stimulating immunoglobulins for Graves disease and no autonomous nodules. Two patients underwent thyroid uptake scans that confirmed thyroiditis. One patient had significantly increased erythrocyte sedimentation rate and interleukin-6. All patients showed improvement in symptoms with nonsteroidal anti-inflammatory drugs, and 1 patient eventually required steroids for symptom control. DISCUSSION: The mRNA vaccine for SARS-CoV-2 was associated with thyroiditis and led to thyrotoxicosis. Elevated proinflammatory markers and cytokines after vaccines may play a major role. CONCLUSION: Our case series report highlights a possible relationship between the COVID-19 mRNA vaccine and thyroiditis with thyrotoxicosis, which has not been recognized by health providers.