Aacute thyroiditis / adverse reaction on thyroid/Thyroid high inflammation; Pain was severe / pain became terrible / pain was very high; pain was more when swallowing; Heart rate was high; Pain in the back of the head; Pain in the neck behind the ears; Pain in both jaws; Fever of 102F; Weakness; Chills; Nausea; fever; This spontaneous case was reported by a consumer and describes the occurrence of THYROIDITIS ACUTE (Aacute thyroiditis / adverse reaction on thyroid/Thyroid high inflammation) in a 37-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 040B21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.    On 14-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 15-Apr-2021, the patient experienced ASTHENIA (Weakness), CHILLS (Chills), NAUSEA (Nausea) and PYREXIA (fever). On 17-Apr-2021, the patient experienced PYREXIA (Fever of 102F). On 19-Apr-2021, the patient experienced NECK PAIN (Pain in the neck behind the ears), PAIN IN JAW (Pain in both jaws) and HEADACHE (Pain in the back of the head). In May 2021, the patient experienced THYROIDITIS ACUTE (Aacute thyroiditis / adverse reaction on thyroid/Thyroid high inflammation) (seriousness criteria hospitalization and medically significant) and HEART RATE INCREASED (Heart rate was high). On an unknown date, the patient experienced PAIN (Pain was severe / pain became terrible / pain was very high) and ODYNOPHAGIA (pain was more when swallowing). The patient was hospitalized from 04-May-2021 to 09-May-2021 due to THYROIDITIS ACUTE. The patient was treated with IBUPROFEN ongoing since an unknown date for Acute thyroiditis, at a dose of 1 dosage form. On 17-Apr-2021, ASTHENIA (Weakness), CHILLS (Chills), NAUSEA (Nausea) and PYREXIA (fever) had resolved. At the time of the report, THYROIDITIS ACUTE (Aacute thyroiditis / adverse reaction on thyroid/Thyroid high inflammation), NECK PAIN (Pain in the neck behind the ears), PAIN IN JAW (Pain in both jaws), PAIN (Pain was severe / pain became terrible / pain was very high), ODYNOPHAGIA (pain was more when swallowing), HEART RATE INCREASED (Heart rate was high), HEADACHE (Pain in the back of the head) and PYREXIA (Fever of 102F) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Body temperature: up to 102 (Inconclusive) Inconclusive. On an unknown date, Computerised tomogram: inconclusive (Inconclusive) Inconclusive. On an unknown date, Heart rate: high (High) High. On an unknown date, SARS-CoV-2 test: negative (Negative) Negative. On an unknown date, Scan thyroid gland: abnormal (abnormal) showed a high inflammation. On an unknown date, Thyroid function test: high (High) High.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Patient has been prescribed steroids for 3-4 days, While on steroids the pain went away but when the treatment was over the pain was very high again.  Company comment: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.   Most recent FOLLOW-UP information incorporated above includes: On 07-Jul-2021: Follow-up received on 07-JUL-2021 included no new information.; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.