Subacute thyroiditis; This literature-non-study case was reported in a literature article and describes the occurrence of THYROIDITIS SUBACUTE (Subacute thyroiditis) in a 42-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.   LITERATURE REFERENCE: A case report of subacute thyroiditis following mRNA COVID-19 vaccine.     The patient's past medical history included Iron deficiency anaemia, Lumbar radiculopathy and Right hemicolectomy in January 2020. Concurrent medical conditions included Adenocarcinoma of colon stage III (Patient was on adjuvant chemotherapy), Paroxysmal supraventricular tachycardia and Chemotherapy induced peripheral neuropathy. Concomitant products included METOPROLOL, FERROUS SULFATE and MULTIVITAMIN & MINERAL for an unknown indication.   On 05-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 05-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On an unknown date,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced THYROIDITIS SUBACUTE (Subacute thyroiditis) (seriousness criterion medically significant). At the time of the report, THYROIDITIS SUBACUTE (Subacute thyroiditis) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In April 2021, Biopsy: she underwent ultrasound-guided fine-needle aspira she underwent ultrasound-guided fine-needle aspiration biopsy of the bilateral 3.4?cm thyroid masses in April 2021. In June 2021, Blood thyroid stimulating hormone (0.350-4.000): 8.80 iu/ml) 8.80 IU/ml). In June 2021, Red blood cell sedimentation rate normal: 14 mm/hour 14 mm/hour. In June 2021, Thyroxine (0.80-2.00): 0.65 ng/dl 0.65 ng/dL. In June 2021, Tri-iodothyronine (0.60-1.81): 1.20 ng/ml 1.20 ng/ml. On an unknown date, Anti-thyroid antibody (Unknown-lessthan 35?iu/ml)): lessthan 10 iu/ml were negative lessthan 10 (<lessthan 35?IU/ml). On an unknown date, Biopsy: biopsy results showed scattered multinucleated gia Biopsy results showed scattered multinucleated giant cells (some with ingested colloid), scattered epithelioid granulomas, groups of follicular cells, scattered lymphocytes, and karyorrhexis.. On an unknown date, Blood creatinine (0.51-0.95): 0.43 mg/dl 0.43 mg/dL. On an unknown date, Blood electrolytes abnormal: normal (normal) Normal. On an unknown date, Blood pressure measurement: 111/75?mm of hg 111/75?mm of Hg. On an unknown date, Blood thyroid stimulating hormone (0.350-4.000): lessthan 0.0005? ?iu/ml lessthan 0.0005??IU/ml and 2.030?iu/ml TSH the week prior to COVID-19 vaccination, obtained as a part of fatigue workup, was 2.030?IU/ml. On an unknown date, Blood urea (7-18): 10?mg/dl 10?mg/dL. On an unknown date, Body temperature: 35.9 degrees celsuis 35.9 degrees celsuis. On an unknown date, Haemoglobin (1.4-15.4): 13.2?g/dl 13.2?g/dL. On an unknown date, Heart rate normal: normal 88 beats/min. On an unknown date, Liver function test: normal (normal) Normal. On an unknown date, Oxygen saturation: 97% on room air 97% on room air. On an unknown date, Physical examination: physical examination was notable for anterior neck Physical examination was notable for anterior neck swelling about 3?cm in size which was tender on palpation.. On an unknown date, Platelet count (150-450): 207 ul 207 uL. On an unknown date, Red blood cell sedimentation rate: 81?mm/hour 81?mm/hour. On an unknown date, Respiratory rate: 17?breaths/min 17?breaths/min. On an unknown date, Thyroxine (0.80-2.00): 1.51?ng/dl 1.51?ng/dL. On an unknown date, Tri-iodothyronine (0.60-1.81): 1.90?ng/dl 1.90?ng/dL. On an unknown date, White blood cell count (3.5-10.0): 6.4 1000/ul 6.4 1000/uL.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered THYROIDITIS SUBACUTE (Subacute thyroiditis) to be related.    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.Patient was presented with anterior neck pain. Patient was treated conservatively with pain medication. Patient was treated with 9 cycles of FOLFOX regimen (fluorouracil, oxaliplatin, and leucovorin) for her colon carcinoma and completed her chemotherapy on 09/2020. 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. The patient denied any family history of head and neck cancer. She denied smoking cigarettes, but drinks alcohol socially. Her home medications included vitamin B12 1000 mcg once daily, ferrous sulfate 325?mg two times a day, and multivitamin capsule 1 capsule daily. Ultrasound of the thyroid revealed a 1.6?×?1.4?×?3.4?cm heterogeneous mass in the right lobe and a 1.6?×?1.8?×?3.4?cm hypoechoic and moderately heterogeneous mass in the left lobe without calcifications, associated with mildly enlarged inferior left paratracheal lymph nodes. The patient was treated with analgesics as needed for pain, until she underwent ultrasound-guided fine-needle aspiration biopsy of the bilateral 3.4?cm thyroid masses in April 2021. These features were consistent with a benign hyperplastic nodule suggestive of subacute (de Quervain) thyroiditis. Cytopathology was benign (Bethesda Category II). During this time period, she had minimal symptoms and was treated with NSAIDs as needed for pain. On a subsequent follow-up visit, 2 months after the biopsy, previously described anterior neck discomfort and earache radiating to the neck resolved.   Most recent FOLLOW-UP information incorporated above includes: On 15-Dec-2021: Follow up received by safety 15-Dec-2021 included an Email with FTA received from team and contain significant information Lab data; Sender's Comments: This literature-non-study case concerns a 42-year-old female patient, with relevant medical history of Adenocarcinoma of colon stage III on adjuvant chemotherapy, who experienced the unexpected AESI event of Subacute thyroiditis. The event occurred approximately 5-6 days after the second dose of mRNA-1273 Vaccine. It was reported that the patient initially presented with bilateral ear pain radiating to the lateral and anterior neck and bilateral lower jaw. The pain was exacerbated by turning her head, swallowing, and coughing. Upon physical examination a 3cm. size anterior neck swelling, which was tender on palpation, was noted. Laboratory examinations done showed lowserum TSH and low serum T3; ESR was also elevated. Thyroid ultrasound revealed a heterogenous mass in each lobe, measuring approximately 3 cm. with enlarged inferior left paratracheal lymph nodes. She then underwent ultrasound-guided fine-needle aspiration biopsy of the bilateral 3.4cm thyroid masses which showed features that were consistent with a benign hyperplastic nodule suggestive of subacute (de Quervain) thyroiditis. During this time, she had minimal symptoms and was treated with NSAIDs as needed for pain. At the time of the report the outcome of the event was resolved. The rechallenge is not applicable since no further dosing is expected. The reporter assessed the events as related to the product. The patient's medical history of Adenocarcinoma of colon stage III on adjuvant chemotherapy, remain as a confounder for the occurrence of the event. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.