Fluid around her heart; Thickening in her intestines; Fever of 101°F; Began vomiting; Having pain in her belly, where her gallbladder is, then complained that it was moving to other side; Felt nauseated/Feel like have to puke; This spontaneous case was reported by a consumer and describes the occurrence of PERICARDIAL EFFUSION (Fluid around her heart) in a 21-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 016B21A and 009C21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Immune system disorder, Kidney stones, Asplenia (No spleen) and IQ test abnormal.   On 30-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 28-May-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 11-May-2021, the patient experienced NAUSEA (Felt nauseated/Feel like have to puke). On 18-Jun-2021, the patient experienced ABDOMINAL PAIN (Having pain in her belly, where her gallbladder is, then complained that it was moving to other side). On 21-Jul-2021, the patient experienced PERICARDIAL EFFUSION (Fluid around her heart) (seriousness criteria hospitalization and medically significant). On 24-Jul-2021, the patient experienced VOMITING (Began vomiting). On 27-Jul-2021, the patient experienced PYREXIA (Fever of 101°F). On an unknown date, the patient experienced GASTROINTESTINAL WALL THICKENING (Thickening in her intestines). The patient was hospitalized from 21-Jul-2021 to 22-Jul-2021 due to PERICARDIAL EFFUSION. The patient was treated with NAPROXEN SODIUM (NAPROXEN [NAPROXEN SODIUM]) ongoing since an unknown date at a dose of 500 mg; COLCHICINE ongoing since an unknown date at a dose of .6 milligram once a day; AMOXICILLIN, CLAVULANATE POTASSIUM (AMOXICILLIN AND CLAVULANATE POTASSIUM [AMOXICILLIN;CLAVULANATE POTASSIUM]) at a dose of 875/125 and Surgery (pericardiocentesis) for Pericardial effusion. At the time of the report, PERICARDIAL EFFUSION (Fluid around her heart), ABDOMINAL PAIN (Having pain in her belly, where her gallbladder is, then complained that it was moving to other side), GASTROINTESTINAL WALL THICKENING (Thickening in her intestines), NAUSEA (Felt nauseated/Feel like have to puke), VOMITING (Began vomiting) and PYREXIA (Fever of 101°F) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 21-Jul-2021, Echocardiogram: abnormal (abnormal) moderate fluid around her heart. On 25-Jul-2021, Bacterial test: negative (Negative) Negative. On 27-Jul-2021, Body temperature: 101 (High) 101 degrees Fahrenheit.         It was reported that there was a little thickening in patient intestines.  Patient took medicine for 4 days, then patient's mother stopped it because doctor was uncertain of cause of thickening. Patient was also prescribed Pepcid, but she's presently not taking.  No concomitant medications were provided; 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.