A Case Report of Subacute Thyroiditis following mRNA COVID-19 Vaccine

Background Subacute thyroiditis has been reported after administration of influenza vaccine. We describe a case of a patient who developed subacute thyroiditis after administration of. Moderna mRNA COVID-19 vaccine. Case Presentation. A 42-year-old female, with a past medical history of stage IIIB pT3N1aM0 right adenocarcinoma of colon status, after right hemicolectomy on 01/2020, followed by adjuvant chemotherapy, paroxysmal supraventricular tachycardia, iron deficiency anemia, chemotherapy-induced neuropathy, and lumbar radiculopathy, presented to our clinic with anterior neck pain that started 6 days after the second dose of Moderna mRNA COVID-19 vaccine. She was diagnosed with subacute thyroiditis and treated conservatively with pain medications. Conclusion Subacute thyroiditis could represent one of the side effects of Moderna mRNA COVID-19 vaccine. Further reports are lacking.


Introduction
Subacute thyroiditis is a well-known clinical diagnosis, usually presenting one to two weeks after an acute viral infection, including COVID-19 [1,2]. Symptoms fluctuate in intensity and last for 3 to 6 weeks. Laboratory investigations show high erythrocyte sedimentation rate (ESR), elevated C-reactive protein (CRP), and suppressed TSH with elevated free T4 and T3 [2]. Treatment with analgesics is recommended, and prednisone if poor improvement [2,3].
Subacute thyroiditis has been reported after administration of influenza and COVID-19 vaccines [1,[4][5][6]. We present a case of subacute thyroiditis after administration of an mRNA COVID-19 vaccine. To our knowledge, this is the first case report of subacute thyroiditis after Moderna mRNA COVID-19 vaccine.

Case Report
A 42-year-old African American female with a past medical history of stage IIIB pT3N1aM0 right adenocarcinoma of colon status after right hemicolectomy on 01/2020, followed by adjuvant chemotherapy, paroxysmal supraventricular tachycardia, iron deficiency anemia, chemotherapy-induced neuropathy, and lumbar radiculopathy, presented to our primary-care clinic on the first week of March 2021 complaining of bilateral ear pain for 2 weeks. e patient was treated with 9 cycles of FOLFOX regimen (fluorouracil, oxaliplatin, and leucovorin) for her colon carcinoma and completed her chemotherapy on 09/ 2020. She received her 1 st dose of Moderna mRNA COVID-19 vaccine on 02/05/2021 and the second dose on 03/05/ 2021. Symptoms started about 5-6 days after the vaccination. She began experiencing right-sided and then leftsided earache radiating down to the lateral and anterior neck and bilateral lower jaw. e pain was exacerbated by turning her head, swallowing, and coughing. She denied fever, fatigue, malaise, anorexia, myalgia, dysphagia, dysphonia, dyspnea cough, rhinorrhea, lacrimation, and ear discharge. She has no history of thyroid disease and/or head and neck radiation exposure. e patient denied any family history of head and neck cancer. She denied smoking cigarettes, but drinks alcohol socially. Her home medications included Metoprolol 25 mg two times a day, vitamin B12 1000 mcg once daily, ferrous sulfate 325 mg two times a day, and multivitamin capsule 1 capsule daily.
Her vitals at the time of presentation were a temperature of 35.9°C, pulse 88 beats/min, blood pressure 111/75 mm of Hg, respiratory rate 17 breaths/min, and oxygen saturation 97% on room air. Physical examination was notable for anterior neck swelling about 3 cm in size which was tender on palpation.

Discussion
Subacute thyroiditis is a relatively uncommon cause of hyperthyroidism that has been associated with upper respiratory viruses, such as influenza, mumps, and other respiratory viruses, but few cases have been reported after inactivated viral vaccines or live-attenuated vaccines such as those for influenza [1,4,5]. is condition is characterized by neck pain, a tender goiter, and a thyroid dysfunction. We present a case of a female with classic symptoms of subacute thyroiditis after Moderna mRNA COVID-19 vaccine administration. yroiditis has been reported as a possible side effect of COVID-19 vaccine in 4 cases thus far [3,5], one case after CoronaVac ® administration [5] and the other with Pfizer mRNA COVID-19 vaccine [3]. Cross recognition between the coronavirus spike protein targeted with mRNA vaccine and thyroid cell antigens is likely the mechanism. Differential diagnosis includes Graves' disease, toxic multinodular goiter, and pharyngitis, but after the administration of a vaccine, subacute thyroiditis should be suspected. Further reports are lacking; however, clinicians should consider subacute thyroiditis after administration of mRNA COVID-19 vaccines as a possible side effect.

Consent
Informed consent for publication was obtained from the patient.

Conflicts of Interest
e authors declare no conflicts of interest.
Acknowledgments is work was supported by the Graduated Medical Education Department of Memorial Healthcare System, Florida.   Case Reports in Endocrinology