pericarditis; felt meh/felt under the weather; Pain in upper left shoulder blade area; Pain in back; Pain in neck; Shallow breathing; chest discomfort/ pressure in left side of chest; This spontaneous case was reported by a consumer and describes the occurrence of PERICARDITIS (pericarditis) in a 22-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 011F21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Fruit allergy (tree fruits). Concomitant products included MOMETASONE FUROATE (FLONASE [MOMETASONE FUROATE]) from 03-Jan-2015 to an unknown date for Seasonal allergy.    On 04-Jan-2022 at 5:15 PM, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 05-Jan-2022, the patient experienced FEELING ABNORMAL (felt meh/felt under the weather), MUSCULOSKELETAL PAIN (Pain in upper left shoulder blade area), BACK PAIN (Pain in back), NECK PAIN (Pain in neck), HYPOPNOEA (Shallow breathing) and CHEST DISCOMFORT (chest discomfort/ pressure in left side of chest). On 05-Jan-2022 at 6:00 PM, the patient experienced PERICARDITIS (pericarditis) (seriousness criterion medically significant). The patient was treated with IBUPROFEN (ADVIL [IBUPROFEN]) for Pericarditis, at an unspecified dose and frequency. At the time of the report, PERICARDITIS (pericarditis) had not resolved and FEELING ABNORMAL (felt meh/felt under the weather), MUSCULOSKELETAL PAIN (Pain in upper left shoulder blade area), BACK PAIN (Pain in back), NECK PAIN (Pain in neck), HYPOPNOEA (Shallow breathing) and CHEST DISCOMFORT (chest discomfort/ pressure in left side of chest) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 06-Jan-2022, Blood test: results not provided Results not provided. On 06-Jan-2022, Chest X-ray: results not provided Results not provided. On 06-Jan-2022, Electrocardiogram: results not provided Results not provided. On an unknown date, Echocardiogram: normal (normal) Normal.         Reported that patient received the Moderna booster shot on Tuesday, 4-Jan-2022. He felt under the weather on Wednesday, but by late evening, he experienced the Pain in upper left shoulder blade area, back and neck. Shallow breathing, pressure in left side of chest Also had chest discomfort.  Reported that on Wednesday night, patient experienced unusual and concerning symptoms  Symptoms of patient worsened so much so that patient ended up (as recommended by our doctor) going to the ER Thursday morning.  Reported that patient was a healthy 22-year-old male. He is a college student and very active. He was in great health prior to the Moderna booster shot. This has completely upended and disrupted his life.   Reported that this situation has not only been a surreal, upsetting, and frightening experience, but also an unexpected one.  Company comment: This case concerns a 22-year-old male patient who experienced serious expected PERICARDITIS one day after the third dose of mRNA-1273. Additional non-serious events were also reported. The patient was treated with IBUPROFEN and at the time of the report outcome had not resolved. The event is consistent with the current understanding of the mechanism of action of mRNA-1273. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.   This case was linked to MOD-2022-445366 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 07-Jan-2022: Follow up report contains no new information. On 11-Jan-2022: Follow up report contains new reporter information , Patient demographic details , lab data result were updated. additional events were updated. and event Outcome updated.; Sender's Comments: This case concerns a 22-year-old male patient who experienced serious expected PERICARDITIS one day after the third dose of mRNA-1273. Additional non-serious events were also reported. The patient was treated with IBUPROFEN and at the time of the report outcome had not resolved. The event is consistent with the current understanding of the mechanism of action of mRNA-1273. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.